Resistin gene variation is associated with systemic inflammation but not plasma adipokine levels, metabolic syndrome or coronary atherosclerosis in nondiabetic Caucasians

Resistin: Potential biomarker and therapeutic target in atherosclerosis

Resistin, a cysteine-rich secretory protein, has a pleiotropic role in humans. Resistin usually presents as trimer or hexamer in plasma, and targets specific receptors Toll Like Receptor 4 (TLR4) or Adenylyl Cyclase-Associated Protein 1 (CAP1). Upon binding to TLR4 and CAP1, resistin can trigger various intracellular signal transduction pathways to induce vascular inflammation, lipid accumulation, and plaque vulnerability. These pro-atherosclerotic effects of resistin appear in various cell types, including endothelial cells, vessel smooth muscle cells and macrophages, which cause diverse damages to cardiovascular system from dyslipidemia, atherosclerosis rupture and ventricular remodeling. In this review, we gather recent evidence about the pro- atherosclerotic effects of resistin and highlight it as a candidate therapeutic or diagnostic target for cardiovascular disease.

The Relevance of Single-nucleotide Polymorphism +62 G>A to the Expression of Resistin Gene Affecting Serum Resistin Levels in Metabolic Syndrome in the Egyptian Population

BACKGROUND

Metabolic Syndrome (MS) is a clinical condition consisting of risk factors associated with type two diabetes and developing cardiovascular disease. It has been suggested that resistin is a linkage between obesity, inflammation and type two diabetes. This study aims to investigate whether Resistin Gene (RETN) polymorphism (+62G>A) is linked to MS and resistin levels among the Egyptian population.

METHODS

This study was performed with 310 Egyptian volunteers: 160 MS subjects and 150 controls. Anthropometric parameters and biochemical variables were determined. The RETN +62G>A polymorphism was 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 liver biomarkers in the MS group. According to RETN +62G>A polymorphism, carriers with the A allele (GA/AA) had significantly increased resistin levels than subjects with the GG genotype, consequently, the RETN +62G >A polymorphism was found to be related to MS, biochemical parameters and anthropometric variables.

CONCLUSION

These findings propose that the RETN +62G>A polymorphism has a great impact on the circulating resistin concentrations, and that resistin levels are strongly related to MS. Therefore, this RETN polymorphism is related to the risk of the prevalence of MS in the Egyptians.

Association of angiotensin-converting enzyme gene I/D polymorphism with chronic obstructive pulmonary disease: a meta-analysis

Objectives:

We conducted a meta-analysis of published studies on the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism associated with the risk of chronic obstructive pulmonary disease, as well as with pulmonary function and circulating angiotensin-converting enzyme changes.

Methods:

A literature search, quality assessment and data extraction were completed independently and in duplicate.

Results:

A total of 16 articles were meta-analysed, including 12 articles (2113 patients and 8786 controls) for chronic obstructive pulmonary disease risk and eight articles (11,664 subjects) for pulmonary and circulating phenotypes. In overall and subgroup analyses, no significance was noted between the I/D polymorphism and chronic obstructive pulmonary disease risk under all genetic models (P>0.05), without heterogeneity or publication bias. Carriers of II, ID and II plus ID genotypes had significantly lower levels of circulating angiotensin-converting enzyme than those with the DD genotype (weighted mean difference −13.35, −8.13 and −10.74 U/L, respectively, P<0.001). For forced expiratory volume in one second (FEV₁)/forced vital capacity, carriers of the DD genotype had marginally lower levels than those with the DD genotype (weighted mean difference –1.66, P=0.034). Furthermore in the case of FEV₁ of 50% or greater of predicted FEV₁, FEV₁ was marginally lower in ID genotype carriers than DD genotype carriers (weighted mean difference −3.50, P=0.056).

Conclusions:

Our meta-analytical findings demonstrated that the ACE gene I/D polymorphism was not associated with the risk of chronic obstructive pulmonary disease.

Association of single nucleotide polymorphisms in resistin gene with rheumatoid arthritis in a Chinese population

BACKGROUND

Recent evidences have revealed that resistin is associated with the development of rheumatoid arthritis (RA). The aim of this study was to analyze the association of resistin gene single nucleotide polymorphisms (SNPs) with RA susceptibility.

METHODS

In this study, we finally analyzed three resistin SNPs (rs1862513, rs3745368, and rs3745367) in 278 RA patients and 276 normal controls recruited from Chinese population using TaqMan SNP genotyping assays.

RESULTS

There were no significant differences for the distribution of allele and genotype frequencies of these three SNPs between RA patients and normal controls (all P > .05). The genotype effects of dominant, recessive models were also analyzed, and no significant association was detected (all P > .05). Haplotype analysis suggested that the frequency of haplotype GAA was notably lower in RA patients in comparison with normal controls (OR = 0.317, 95% CI: 0.125-0.807, P = .011).

CONCLUSION

In a ward, our results indicated that resistin gene polymorphisms might affect the genetic predisposition of RA in Chinese population.

Association between Two Resistin Gene Polymorphisms and Metabolic Syndrome in Jilin, Northeast China: A Case-Control Study

Metabolic syndrome (MetS) is a significant health care problem worldwide and is characterized by increased fasting glucose and obesity. Resistin is a protein hormone produced both by adipocytes and immunocompetent cells, including those residing in adipose tissue, and is believed to modulate glucose tolerance and insulin action. This study examined the association of resistin gene polymorphisms, rs1862513 and rs3745368, and related haplotypes with the development of metabolic syndrome in a Han Chinese population. This case-control study was performed on 3792 subjects, including 1771 MetS cases and 2021 healthy controls from the Jilin province of China. Metabolic syndrome was defined according to the criteria of the International Diabetes Federation (IDF). Logistic regression analysis was used to estimate the relationship between gene polymorphism and MetS. Our results showed that there were no significant associations between MetS and the genotype distributions in four kinds of inheritance models, allele frequencies, and related haplotypes of resistin gene polymorphisms rs1862513 and rs3745368 (all p values > 0.05). Based on our study findings, we concluded that mutations in resistin genes are not associated with the presence of MetS in a Han Chinese population from Jilin province in China.

The rs1862513 Variant in Resistin Gene-Modified Insulin Resistance and Insulin Levels after Weight Loss Secondary to Hypocaloric Diet

BACKGROUND/AIMS

Polymorphisms of a single nucleotide in RETN have been associated with indexes of insulin resistance. Our aim was to analyze the effects of the rs1862513 RETN gene polymorphism on insulin resistance, insulin levels, and resistin levels changes after 3 months of a low-fat hypocaloric diet.

DESIGN

A Caucasian population of 133 obese patients was analyzed before and after 3 months on a low-fat hypocaloric diet.

RESULTS

Fifty-six patients (42.1%) had the genotype GG (wild group) and 77 (57.9%) patients had the other genotypes; GC (59 patients, 44.4%) or CC (18 patients, 13.5%; mutant group). In wild and mutant genotype groups, weight, body mass index, fat mass, waist circumference, and systolic blood pressure decreased. In the wild genotype group, the decrease in total cholesterol was -13.1 ± 25.3 mg/dL (vs. -4.4 ± 13.7 mg/dL in mutant group: p = 0.004 for group deltas), low density lipoprotein (LDL)-cholesterol was -13.0 ± 21.5 mg/dL (-4.3 ± 10.5 mg/dL: p = 0.007), glucose -7.2 ± 3.5 mg/dL (-0.8 ± 0.2 mg/dL: p = 0.01), insulin -5.6 ± 2.5 mUI/L (-2.9 ± 1.2 mUI/L: p = 0.03) and homeostasis model assessment-insulin resistance (HOMA-IR) -2.5 ± 1.1 (-0.6 ± 1.4: p = 0.02). Leptin levels decreased in both genotypes (-10.1 ± 9.5 ng/dL in wild type group vs. -13.1 ± 0.2 ng/dL in mutant type group: p > 0.05).

CONCLUSION

The present study suggests that the G/G genotype of RETN rs1862513 could be a predictor of the reduction of HOMA-IR, insulin, fasting glucose and LDL cholesterol secondary to a hypocaloric diet in obese subjects.

The role of adipokines in the rapid antidepressant effects of ketamine

We previously found that body mass index (BMI) strongly predicted response to ketamine. Adipokines have a key role in metabolism (including BMI). They directly regulate inflammation and neuroplasticity pathways and also influence insulin sensitivity, bone metabolism and sympathetic outflow; all of these have been implicated in mood disorders. Here, we sought to examine the role of three key adipokines-adiponectin, resistin and leptin-as potential predictors of response to ketamine or as possible transducers of its therapeutic effects. Eighty treatment-resistant subjects who met DSM-IV criteria for either major depressive disorder (MDD) or bipolar disorder I/II and who were currently experiencing a major depressive episode received a single ketamine infusion (0.5 mg kg-1 for 40 min). Plasma adipokine levels were measured at three time points (pre-infusion baseline, 230 min post infusion and day 1 post infusion). Overall improvement and response were assessed using percent change from baseline on the Montgomery-Asberg Depression Rating Scale and the Hamilton Depression Rating Scale. Lower baseline levels of adiponectin significantly predicted ketamine's antidepressant efficacy, suggesting an adverse metabolic state. Because adiponectin significantly improves insulin sensitivity and has potent anti-inflammatory effects, this finding suggests that specific systemic abnormalities might predict positive response to ketamine. A ketamine-induced decrease in resistin was also observed; because resistin is a potent pro-inflammatory compound, this decrease suggests that ketamine's anti-inflammatory effects may be transduced, in part, by its impact on resistin. Overall, the findings suggest that adipokines may either predict response to ketamine or have a role in its possible therapeutic effects.

Adipokine Gene Single-Nucleotide Polymorphisms in Portuguese Obese Adolescents: Associations with Plasma Concentrations of Adiponectin, Resistin, IL-6, IL-1β, and TNF-α

BACKGROUND

The genetic contribution to obesity and to circulating adipokine levels has not been completely clarified. We aimed to evaluate adipokine genes' single-nucleotide polymorphism (SNP) prevalence and its association with circulating adipokine levels and risk factors for cardiovascular disease in an obese Portuguese pediatric population.

METHODS

Two hundred forty-eight obese adolescents (mean age 13.4 years old; 47.2% females) participated in a cohort study. We screened 12 SNPs by direct sequencing in five adipokine genes: adiponectin (ADIPOQ: rs16861194, rs17300539, rs266729, rs2241766, rs1501299), interleukin-1β (IL-1β; rs1143627), IL-6 (IL-6; rs1800795), tumor necrosis factor-α (TNF-α; rs1800629), and resistin (RETN; rs1862513, rs3219177, rs3745367, rs3745368). Biochemical analysis included determination of circulating adipokines, C-reactive protein (CRP) levels, lipid profile, and markers of insulin resistance.

RESULTS

Compared to males, females presented higher circulating levels of insulin, adiponectin, IL-6, resistin, and leptin concentrations, but lower TNF-α levels. No statistically significant differences were found for genotype or allelic distributions between genders. In the whole sample population, adiponectin levels were influenced by ADIPOQ rs17300539 (c.-1138G>A; lower in subjects with GG genotype). When only males were considered, IL-1β, IL-6, and TNF-α levels were associated with ADIPOQ rs1501299 (c.214 + 62G>T; higher in GG subjects). TNF-α concentrations were modulated by TNF-α rs1800629 (c.-488G>A; lower in GG males), RETN rs1862513 (c.-216C>G; higher in CC subjects), and RETN rs3219177 (c.118 + 39C>T; higher in CC subjects). Leptin levels were influenced by IL-1β rs1143627 (c.-118C>T) presenting TT individuals' lower levels.

CONCLUSIONS

Our data demonstrate that in pediatric obese patients, some adipokine gene SNPs have an association with circulating adipokine levels and lipid profile.

Resistin's, obesity and insulin resistance: the continuing disconnect between rodents and humans

PURPOSE

This review aimed to discuss the conflicting findings from resistin research in rodents and humans as well as recent advances in our understanding of resistin's role in obesity and insulin resistance.

METHODS

A comprehensive review and synthesis of resistin's role in obesity and insulin resistance as well as conflicting findings from resistin research in rodents and humans.

RESULTS

In rodents, resistin is increased in high-fat/high-carbohydrate-fed, obese states characterized by impaired glucose uptake and insulin sensitivity. Resistin plays a causative role in the development of insulin resistance in rodents via 5' AMP-activated protein kinase (AMPK)-dependent and AMPK-independent suppressor of cytokine signaling-3 (SOCS-3) signaling. In contrast to rodents, human resistin is primarily secreted by peripheral-blood mononuclear cells (PBMCs) as opposed to white adipocytes. Circulating resistin levels have been positively associated with central/visceral obesity (but not BMI) as well as insulin resistance, while other studies show no such association. Human resistin has a role in pro-inflammatory processes that have been conclusively associated with obesity and insulin resistance. PBMCs, as well as vascular cells, have been identified as the primary targets of resistin's pro-inflammatory activity via nuclear factor-κB (NF-κB, p50/p65) and other signaling pathways.

CONCLUSION

Mounting evidence reveals a continuing disconnect between resistin's role in rodents and humans due to significant differences between these two species with respect to resistin's gene and protein structure, differential gene regulation, tissue-specific distribution, and insulin resistance induction as well as a paucity of evidence regarding the resistin receptor and downstream signaling mechanisms of action.

The role of adipokines in ischemic stroke risk stratification

Background

Adiponectin, leptin, and resistin are the most well-studied adipokines and play important roles in the regulation of glucose metabolism, subclinical inflammation, and cardiovascular homeostasis. Accordingly, measurement of adipokine levels might be useful in cardiovascular risk stratification. Moreover, the study of single-nucleotide polymorphisms of genes that encode these adipokines might also represent a valuable predictive tool in cardiovascular disease prevention strategies.

Aims

To summarize the biologic role of the adipokines adiponectin, leptin, and resistin and the prognostic value of their serum levels regarding the occurrence and outcome of ischemic stroke. We also discuss the relationship of single-nucleotide polymorphisms of the adiponectin, leptin genes, and the −420C > G polymorphism of resistin gene with stroke risk.

Summary of review

Several studies in the general population evaluated the association between these adipokines and stroke risk, yielding conflicting results. There are more limited data regarding the effect of these adipokines on stroke severity and outcome. A small number of studies also assessed the predictive role of single-nucleotide polymorphisms of the adiponectin, leptin, and resistin genes regarding stroke risk, but the findings were also controversial.

Conclusions

It is unclear whether adiponectin, leptin, and resistin levels or the single-nucleotide polymorphisms of their encoding genes are independently associated with stroke risk. However, given the role of these adipokines in the pathogenesis of atherosclerosis, larger prospective studies, both in the general population and in patients with a history of stroke, are needed to determine whether the measurement of serum levels of these adipokines or the evaluation of single-nucleotide polymorphisms in their encoding genes could improve stroke risk prediction. If this relationship is proven, therapeutic interventions targeting adipokine levels might represent a novel approach to reduce stroke-related mortality and disability.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

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.

The association of resistin with cardiovascular disease in the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

To describe the relationship between circulating resistin levels and cardiovascular diseases (CVD) and all-cause death in a multi-ethnic cohort.

METHODS AND RESULTS

We studied 1913 participants from the Multi-Ethnic Study of Atherosclerosis with measurements of plasma resistin levels. Absolute proportions experiencing new-onset atrial fibrillation (AF), atherosclerotic CVD (myocardial infarction, angina, resuscitated cardiac arrest, stroke), heart failure (HF), and all-cause death were calculated for each quartile of resistin. We used adjusted Cox proportional regression modeling resistin as a continuous variable per standard deviation of log-transformed resistin and secondarily as a categorical variable using resistin quartiles. Results were stratified by sex and race/ethnicity. The mean age of the population was 64.5 ± 10 years with half being female and a median resistin concentration of 15.1 ng/mL (11.9-19.1). Mean follow-up time was 7.2 ± 1.8 years. There was a graded increase in the occurrence of all outcomes across increasing quartiles of resistin. Modeled as a continuous variable, after adjustment for anthropomorphic measures, traditional risk factors, markers of inflammation, and other adipokines, significant associations were noted for HF (HR 1.4, CI 1.0-2.0), hard and all CVD (HR 1.3, 1.1-1.7 and 1.3, 1.1-1.6, respectively), and CHD (HR 1.31, 1.0-1.6), but not for AF or death. Significant interaction terms were noted between resistin and race, with Hispanic race/ethnicity showing the strongest relationship between resistin and outcomes.

CONCLUSIONS

In an ethnically diverse population without known CVD at baseline, there was a strong, independent association between higher resistin levels and incident CVD, CHD and HF.

Resistin in rodents and humans

Obesity is characterized by excess accumulation of lipids in adipose tissue and other organs, and chronic inflammation associated with insulin resistance and an increased risk of type 2 diabetes. Obesity, type 2 diabetes, and cardiovascular diseases are major health concerns. Resistin was first discovered as an adipose-secreted hormone (adipokine) linked to obesity and insulin resistance in rodents. Adipocyte-derived resistin is increased in obese rodents and strongly related to insulin resistance. However, in contrast to rodents, resistin is expressed and secreted from macrophages in humans and is increased in inflammatory conditions. Some studies have also suggested an association between increased resistin levels and insulin resistance, diabetes and cardiovascular disease. Genetic studies have provided additional evidence for a role of resistin in insulin resistance and inflammation. Resistin appears to mediate the pathogenesis of atherosclerosis by promoting endothelial dysfunction, vascular smooth muscle cell proliferation, arterial inflammation, and formation of foam cells. Indeed, resistin is predictive of atherosclerosis and poor clinical outcomes in patients with coronary artery disease and ischemic stroke. There is also growing evidence that elevated resistin is associated with the development of heart failure. This review will focus on the biology of resistin in rodents and humans, and evidence linking resistin with type 2 diabetes, atherosclerosis, and cardiovascular disease.

Resistin in serum and gingival crevicular fluid as a marker of periodontal inflammation and its correlation with single-nucleotide polymorphism in human resistin gene at -420

AIMS

Resistin is an adipocytokine, which have been studied for its role in insulin resistance and recently in inflammation. The aim of the present study is to assess the concentration of resistin in serum and gingival crevicular fluid (GCF) and to compare the levels between subjects with and without periodontitis and type 2 diabetes mellitus (T2DM) and to further correlate the resistin levels with the single-nucleotide polymorphism (SNP) at -420.

SETTING AND DESIGNS

A total of 96 subjects (48 males and 48 females) were divided on the basis of gingival index (GI), probing pocket depth (PD), clinical attachment level (CAL) and hemoglobin A1c levels into healthy (group 1, n = 24), uncontrolled-diabetes related periodontitis (group 2, n = 24), controlled-diabetes related periodontitis (group 3, n = 24) and chronic periodontitis without T2DM (group 4, n = 24).

MATERIALS AND METHODS

The GCF and serum levels of resistin were quantified using the enzyme-linked immunosorbent assay and compared among the study groups. Further, the association of the resistin levels with periodontal inflammation and SNP at -420 was studied.

RESULTS AND CONCLUSION

The resistin levels in GCF and serum from patients with periodontitis or diabetes mellitus related periodontitis (controlled or uncontrolled) were higher than that of healthy subjects and correlated positively with GI. Further, subjects with GG genotype at -420 showed significantly higher GI, PD, CAL as compared with genotype group CC. Resistin was detected in all serum and GCF samples and was significantly higher in periodontitis. Further, GG genotype at -420 was associated significantly with periodontal inflammation and resistin levels.

Expression of the adipocytokine resistin and its association with the clinicopathological features and prognosis of pancreatic ductal adenocarcinoma

Fat tissue is viewed as an active endocrine organ that secretes a variety of bioactive substances. Resistin, an adipocyte-secreted factor, is thought to be closely related to obesity, insulin resistance and inflammation, the three most significant risk factors for the progression of pancreatic cancer. However, the association between resistin and pancreatic cancer is still unknown. In this study, pancreatic tumor samples from 45 patients with pancreatic ductal adenocarcinoma were analyzed with immunohistochemistry for the expression of resistin. The correlation between resistin expression and clinicopathological features and prognosis were evaluated. Resistin staining was observed in 48.9% (22 of 45) of the cases. Resistin expression was more frequent in poorly differentiated tumors (9 of 9, 100%) compared to moderately differentiated tumors (11 of 28, 39.3%) and well-differentiated tumors (2 of 8, 25%) (p<0.01). The incidence of resistin expression in patients with Japan Pancreas Society stages III-IV (18 of 27, 66.7%) was significantly higher than in subjects with stages I-II (4 of 18, 22.2%) (p<0.01). Patients with resistin-stained tumors had significantly shorter relapse-free survival times (median, 9 months) than patients with negative tumors (median, 18 months) (p<0.05). In addition, multivariate analysis showed that resistin expression was an independent prognostic factor for relapse-free survival of patients with pancreatic ductal adenocarcinoma (p<0.05). These results demonstrate that resistin may influence the progression of pancreatic tumors and may be a useful predictor of relapse-free survival in patients with pancreatic ductal adenocarcinoma.

Genetic markers of cardiovascular disease in rheumatoid arthritis

Cardiovascular (CV) disease is the most common cause of premature mortality in patients with rheumatoid arthritis (RA). It is the result of an accelerated atherosclerotic process. Both RA and atherosclerosis are complex polygenic diseases. Besides traditional CV risk factors and chronic inflammation, a number of studies have confirmed the role of genetic factors in the development of the atherogenesis observed in RA. In this regard, besides a strong association between the HLA-DRB1∗04 shared epitope alleles and both endothelial dysfunction, an early step in the atherosclerotic process, and clinically evident CV disease, other polymorphisms belonging to genes implicated in inflammatory and metabolic pathways, located inside and outside the HLA region, such as the 308 variant (G > A, rs1800629) of the TNFA locus, the rs1801131 polymorphism (A > C; position + 1298) of the MTHFR locus, or a deletion of 32 base pairs on the CCR5 gene, seem to be associated with the risk of CV disease in patients with RA. Despite considerable effort to decipher the genetic basis of CV disease in RA, further studies are required to better establish the genetic influence in the increased risk of CV events observed in patients with RA.

Genetic variants and the metabolic syndrome: a systematic review

Several candidate gene studies on the metabolic syndrome (MetS) have been conducted. However, for most single nucleotide polymorphisms (SNPs) no systematic review on their association with MetS exists. A systematic electronic literature search was conducted until the 2nd of June 2010, using HuGE Navigator. English language articles were selected. Only genes of which at least one SNP-MetS association was studied in an accumulative total population ≥ 4000 subjects were included. Meta-analyses were conducted on SNPs with three or more studies available in a generally healthy population. In total 88 studies on 25 genes were reviewed. Additionally, for nine SNPs in seven genes (GNB3, PPARG, TCF7L2, APOA5, APOC3, APOE, CETP) a meta-analysis was conducted. The minor allele of rs9939609 (FTO), rs7903146 (TCF7L2), C56G (APOA5), T1131C (APOA5), C482T (APOC3), C455T (APOC3) and 174G>C (IL6) were more prevalent in subjects with MetS, whereas the minor allele of Taq-1B (CETP) was less prevalent in subjects with the MetS. After having systematically reviewed the most studied SNP-MetS associations, we found evidence for an association with the MetS for eight SNPs, mostly located in genes involved in lipid metabolism.

Human resistin: found in translation from mouse to man

The discovery of resistin 10 years ago as a fat cell-secreted factor that modulates insulin resistance suggested a link to the current obesity-associated epidemics of diabetes and cardiovascular disease, which are major human health concerns. Although adipocyte-derived resistin is indisputably linked to insulin resistance in rodent models, the relevance of human resistin is complicated because human resistin is secreted by macrophages rather than adipocytes, and because of the descriptive nature of human epidemiology. In this review, we examine the recent and growing evidence that human resistin is an inflammatory biomarker and a potential mediator of diabetes and cardiovascular disease.

Plasma levels of resistin-like molecule beta in humans

BACKGROUND

Resistin-like molecules (RELM) are expressed in many tissues and among those, RELMβ is most abundantly expressed in the colon. Based on animal studies, RELMβ is induced by high fat diets, obesity, and intestinal microflora and may play a role in insulin resistance and intestinal inflammation. In the present study, we evaluated whether RELMβ could be measured in human plasma and the influence of selected host and behavioral factors on RELMβ levels, including known risk factors for colorectal cancer.

METHODS

The subjects for this pilot study were derived from healthy controls who participated in a population-based case-control study of colorectal cancer in Metropolitan Detroit. The subjects were 45-80 years of age without history of cancer or colorectal resection.

RESULTS

RELMβ was present in human plasma, with levels in the range of 0.08-0.26 ng/mL. Lower RELMβ levels were found in subjects with non-Caucasian race, lower pack-years of smoking, and higher physical activity index scores. Other variables such as dietary intakes, gender, obesity, use of non-steroidal anti-inflammatory agents and history of polyps were not associated with RELMβ levels.

CONCLUSIONS

The direct association of RELMβ with smoking and inverse association with physical activity, both of which are risk factors for colon cancer, indicates that RELMβ may be involved in mediating the effects of these two lifestyle factors on risk of colon cancer.

Adipocytokines and the metabolic syndrome among older persons with and without obesity: the InCHIANTI study

OBJECTIVES

Adipose tissue-derived inflammation may contribute to metabolic alterations and eventually to the metabolic syndrome (MetS). The purpose of this study was to: (1) examine the role of adipocytokines in the association between obesity and the MetS and (2) to determine whether the association is different in obese and non-obese persons.

DESIGN

Cross-sectional population-based InCHIANTI study.

SUBJECTS

A total of 944 community-dwelling adults aged 65 years and older living in Tuscany, Italy.

MEASUREMENTS

Obesity was defined as body mass index > or =30 kg/m2 and MetS as > or =3 of the ATP-III criteria. Circulating levels of C-reactive protein, interleukin (IL)-6, IL-1 receptor antagonist (IL-1ra), IL-18, tumour necrosis factor (TNF)-alpha R1, adiponectin, resistin and leptin were measured. Additionally, insulin resistance was determined using the homeostasis model assessment (HOMA-IR).

RESULTS

The prevalence of the MetS was 32%. Both overall and abdominal obesity were significantly associated with the MetS after adjusting for inflammatory cytokines, adipokines and lifestyle factors. After adjusting for multiple confounders and HOMA-IR, IL-1ra, TNF-alpha R1 and adiponectin (P < 0.05) remained significantly associated with the MetS. Having multiple cytokines in the highest tertile increased the likelihood of having the MetS in both obese (P for trend 0.002) and non-obese persons (P for trend 0.001) independent of insulin resistance.

CONCLUSIONS

Non-obese and obese individuals who develop an intense pro-inflammatory state may be more prone to develop the MetS than those with lower levels of inflammation.