Association of adiponectin, resistin, and vascular inflammation: analysis with 18F-fluorodeoxyglucose positron emission tomography

Inflammatory markers and body mass index amoung hispanic children

BACKGROUND AND OBJECTIVES

Body mass index (BMI) is inversely proportional with adiponectin levels among adults, while insulin, C-reactive protein (CRP), interleukin 6 (IL-6), resistin and tumor necrosis factor-alpha (TNF-α) have been linked with elevated BMI. The role and relation of these biomarkers with BMI among a Hispanic pediatric population are less known. Thus, the objective of this study was to examine the association of inflammatory markers with the odds of overweight/obesity while controlling for several sociodemographic factors among a Hispanic youth population in Northeast Tennessee.

METHODS

Height, weight, demographic information, and blood samples were collected from 107 Hispanic children aged 2 to 10 years recruited at a large community health center in 2015-2016 in Northeast Tennessee. Data for this research were accessed and analyzed in 2022. Multivariable logistic regression was conducted to assess the relations between adiponectin, insulin, resistin, CRP, TNF-α, and IL-6, and overweight/obesity vs. having a healthy (normal) weight.

RESULTS

Adiponectin levels were significantly lower among overweight/obese Hispanic children (p = 0.0144) compared to healthy weight children. The odds of overweight/obesity decreased by 4% for every one-unit increase in serum adiponectin. Insulin levels were significantly higher among overweight/obese Hispanic children compared to healthy weight children (p = 0.0048). The odds of overweight/obesity increased by 7% for every one-unit increase in serum insulin. Resistin, IL-6, TNF-α, and CRP were not significantly associated with overweight/obesity in this population.

CONCLUSION

Adiponectin behaves similarly in Hispanic youth as it does in other pediatric populations, possibly making it a valuable marker when examining metabolic health status in this population.

Interplay of skeletal muscle and adipose tissue: sarcopenic obesity

Sarcopenic obesity is becoming a global health concern, owing to the rising older population, causing cardiometabolic morbidity and mortality. Loss of muscle exceeding normal age-related changes has been revealed to be associated with obesity, aggravating each other through complex interactions. Physiological regeneration and proliferation of muscle tissue are achieved through harmonious processes of regulated inflammation, autophagy, muscle satellite cell proliferation, and signaling molecule function. Adipokines and myokines are signaling molecules from adipose tissue and muscle, respectively, that exert autocrine, paracrine, and endocrine effects on fat and muscle tissues. These signaling molecules interact with each other to regulate metabolic homeostasis. However, excessive adiposity creates pro-inflammatory conditions, leading to metabolic disorders and the disorganization of systemic homeostasis. Therefore, obesity impedes muscle tissue regeneration and induces the loss of muscle mass and function. Numerous studies have attempted to demonstrate the pathophysiological interaction between sarcopenia and obesity, but the interwoven matrix of the relationship between myokines and adipokines has made it difficult for researchers to understand them. This review briefly describes updated information about the crosstalk between muscle and adipose tissue.

Visceral adipose tissue phenotype and hypoadiponectinemia are associated with aortic Fluorine-18 fluorodeoxyglucose uptake in patients with familial dyslipidemias

BACKGROUND

The role of adipose tissue (AT) in arterial inflammation in familial dyslipidaemias is poorly studied. We investigated the relationship between AT and arterial inflammation in patients with heterozygous familial hypercholesterolemia (heFH) and familial combined hyperlipidemia (FCH).

METHODS AND RESULTS

A total of 40 patients (20 heFH/20 FCH) and a subgroup of 20 of non-heFH/FCH patients were enrolled. Participants underwent blood sampling for serum adipokine measurements and Fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT imaging. Abdominal visceral (VAT) and subcutaneous (SAT) AT volumes and AT and abdominal aorta 18F-FDG uptake were quantified. FCH patients had increased VAT (pANOVA = 0.004) and SAT volumes (pANOVA = 0.003), lower VAT metabolic activity (pANOVA = 0.0047), and lower adiponectin levels (pANOVA = 0.007) compared to heFH or the control group. Log(Serum adiponectin) levels were correlated with aortic TBR (b = - 0.118, P = 0.038). In mediation analysis, VAT volume was the major determinant of circulating adiponectin, an effect partly mediated via VAT TBR. Clustering of the population of heFH/FCH by VAT volume/TBR and serum adiponectin identified two distinct patient clusters with significant differences in aortic TBR levels (2.11 ± 0.06 vs 1.89 ± 0.05, P= 0.012).

CONCLUSIONS

VAT phenotype (increased VAT volume and/or high VAT TBR) and hypoadiponectinemia may account for the observed differences in arterial inflammation levels between heFH and FCH patients.

Progression of Early Subclinical Atherosclerosis (PESA) Study: JACC Focus Seminar 7/8

Atherosclerosis starts early in life and progresses silently for decades. Considering atherosclerosis as a "systemic disease" invites the use of noninvasive methodologies to detect disease in various regions before symptoms appear. The PESA-(Progression of Early Subclinical Atherosclerosis) CNIC-SANTANDER study is an ongoing prospective cohort study examining imaging, biological, and behavioral parameters associated with the presence and progression of early subclinical atherosclerosis. Between 2010 and 2014, PESA enrolled 4,184 asymptomatic middle-aged participants who undergo serial 3-yearly follow-up examinations including clinical interviews, lifestyle questionnaires, sampling, and noninvasive imaging assessment of multiterritorial subclinical atherosclerosis (carotids, iliofemorals, aorta, and coronaries). PESA tracks the trajectories of atherosclerosis and associated disorders from early stages to the transition to symptomatic phases. A joint venture between the CNIC and the Santander Bank, PESA is expected to run until at least 2029, and its significant contributions to date are presented in this review paper.

Atherosclerosis imaging using PET: Insights and applications

PET imaging is able to harness biological processes to characterise high-risk features of atherosclerotic plaque prone to rupture. Current radiotracers are able to track inflammation, microcalcification, hypoxia, and neoangiogenesis within vulnerable plaque. 18 F-fluorodeoxyglucose (18 F-FDG) is the most commonly used radiotracer in vascular studies and is employed as a surrogate marker of plaque inflammation. Increasingly, 18 F-FDG and other PET tracers are also being used to provide imaging endpoints in cardiovascular interventional trials. The evolution of novel PET radiotracers, imaging protocols, and hybrid scanners are likely to enable more efficient and accurate characterisation of high-risk plaque. This review explores the role of PET imaging in atherosclerosis with a focus on PET tracers utilised in clinical research and the applications of PET imaging to cardiovascular drug development.

Vascular Inflammation in Subclinical Atherosclerosis Detected by Hybrid PET/MRI

BACKGROUND

Atherosclerosis is a chronic inflammatory disease, but data on arterial inflammation at early stages is limited.

OBJECTIVES

The purpose of this study was to characterize vascular inflammation by hybrid ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/magnetic resonance imaging (PET/MRI).

METHODS

Carotid, aortic, and ilio-femoral ¹⁸F-FDG PET/MRI was performed in 755 individuals (age 40 to 54 years; 83.7% men) with known plaques detected by 2-/3-dimensional vascular ultrasound and/or coronary calcification in the PESA (Progression of Early Subclinical Atherosclerosis) study. The authors evaluated the presence, distribution, and number of arterial inflammatory foci (increased ¹⁸F-FDG uptake) and plaques with or without inflammation (coincident ¹⁸F-FDG uptake).

RESULTS

Arterial inflammation was present in 48.2% of individuals (24.4% femorals, 19.3% aorta, 15.8% carotids, and 9.3% iliacs) and plaques in 90.1% (73.9% femorals, 55.8% iliacs, and 53.1% carotids). ¹⁸F-FDG arterial uptakes and plaques significantly increased with cardiovascular risk factors (p < 0.01). Coincident ¹⁸F-FDG uptakes were present in 287 of 2,605 (11%) plaques, and most uptakes were detected in plaque-free arterial segments (459 of 746; 61.5%). Plaque burden, defined by plaque presence, number, and volume, was significantly higher in individuals with arterial inflammation than in those without (p < 0.01). The number of plaques and ¹⁸F-FDG uptakes showed a positive albeit weak correlation (r = 0.25; p < 0.001).

CONCLUSIONS

Arterial inflammation is highly prevalent in middle-aged individuals with known subclinical atherosclerosis. Large-scale multiterritorial PET/MRI allows characterization of atherosclerosis-related arterial inflammation and demonstrates ¹⁸F-FDG uptake in plaque-free arterial segments and, less frequently, within plaques. These findings suggest an arterial inflammatory state at early stages of atherosclerosis. (Progression of Early Subclinical Atherosclerosis [PESA]; NCT01410318).

Organokines in disease

Studies have linked obesity, metabolic syndrome, type 2 diabetes, cardiovascular disease (CVD), nonalcoholic fatty liver disease (NAFLD) and dementia. Their relationship to the incidence and progression of these disease states suggests an interconnected pathogenesis involving chronic low-grade inflammation and oxidative stress. Metabolic syndrome represents comorbidities of central obesity, insulin resistance, dyslipidemia, hypertension and hyperglycemia associated with increased risk of type 2 diabetes, NAFLD, atherosclerotic CVD and neurodegenerative disease. As the socioeconomic burden for these diseases has grown signficantly with an increasing elderly population, new and alternative pharmacologic solutions for these cardiometabolic diseases are required. Adipose tissue, skeletal muscle and liver are central endocrine organs that regulate inflammation, energy and metabolic homeostasis, and the neuroendocrine axis through synthesis and secretion of adipokines, myokines, and hepatokines, respectively. These organokines affect each other and communicate through various endocrine, paracrine and autocrine pathways. The ultimate goal of this review is to provide a comprehensive understanding of organ crosstalk. This will include the roles of novel organokines in normal physiologic regulation and their pathophysiological effect in obesity, metabolic syndrome, type 2 diabetes, CVD, NAFLD and neurodegenerative disorders.

TSH suppression aggravates arterial inflammation - an 18F-FDG PET study in thyroid carcinoma patients

Purpose

We aimed to investigate the influence of both hypothyroidism and thyroid-stimulating hormone (TSH) suppression on vascular inflammation, as assessed with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT).

Methods

Ten thyroid carcinoma patients underwent an ¹⁸F-FDG PET/CT during post-thyroidectomy hypothyroidism and during thyrotropin (TSH) suppression after ¹³¹I (radioiodine) ablation therapy. We analysed the ¹⁸F-FDG uptake in the carotids, aortic arch, ascending, descending, and abdominal aorta to investigate the effects of thyroid hormone status on arterial inflammation. Target-to-background ratios (TBRs) corrected for blood pool activity were established for all arterial territories. Results were further compared to euthyroid historic control subjects.

Results

In general, there was a trend towards higher vascular TBRs during TSH suppression than during hypothyroidism (TBR_max all vessels = 1.6 and 1.8, respectively, p = 0.058), suggesting a higher degree of arterial inflammation. In concurrence with this, we found increased C-reactive protein (CRP) levels after levothyroxine treatment (CRP = 2.9 mg/l and 4.8 mg/l, p = 0.005). An exploratory comparison with euthyroid controls showed significant higher TBRs during TSH suppression for the carotids, aortic arch, thoracic descending aorta, and when all vascular territories were combined (TBR_maxp = 0.013, p = 0.016, p = 0.030 and p = 0.018 respectively).

Conclusions

Arterial inflammation is increased during TSH suppression. This finding sheds new light on the underlying mechanism of the suspected increased risk of cardiovascular disease in patients with TSH suppression.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-04292-w) contains supplementary material, which is available to authorized users.

Diet-Modulated Lipoprotein Metabolism and Vascular Inflammation Evaluated by 18F-fluorodeoxyglucose Positron Emission Tomography

Vascular inflammation plays a central role in atherosclerosis, from initiation and progression to acute thrombotic complications. Modified low-density lipoproteins (LDLs) and apoB-containing particles stimulate plaque inflammation by interacting with macrophages. Loss of function of high-density lipoprotein (HDL) for preventing LDL particles from oxidative modification in dyslipidemic states may amplify modified LDL actions, accelerating plaque inflammation. Diets are one of the most important factors that can affect these processes of lipoprotein oxidation and vascular inflammation. Recently, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a reliable noninvasive imaging modality for identifying and quantifying vascular inflammation within atherosclerotic lesions based on the high glycolytic activity of macrophages infiltrating active atherosclerotic plaques. Vascular inflammation evaluated by FDG PET has been positively related to metabolic syndrome components and traditional risk factors of cardiovascular disease, including high-sensitivity C-reactive protein, body mass index, and insulin resistance. A positive association of vascular inflammation with endothelial dysfunction, resistin levels, pericardial adipose tissue, and visceral fat area has also been reported. In contrast, HDL cholesterol and adiponectin have been inversely related to vascular inflammation detected by FDG PET. Because of its reproducibility, serial FDG PET shows potential for tracking the effects of dietary interventions and other systemic and local antiatherosclerotic therapies for plaque inflammation.

Carnosine Supplementation Improves Serum Resistin Concentrations in Overweight or Obese Otherwise Healthy Adults: A Pilot Randomized Trial

Adipokines play an important role in the regulation of glucose metabolism. We have previously shown that carnosine supplementation in overweight or obese non-diabetic individuals improves glucose metabolism but does not change adiponectin concentrations. However, its effect on other adipokines has not been investigated. Herein we further determined the effect of carnosine supplementation on serum adipsin, resistin and leptin. Twenty-two overweight or obese otherwise healthy adults were randomly assigned to receive either 2 g of carnosine (n = 13) or identically looking placebo (n = 9) for 12 weeks. Serum adipsin, leptin and resistin were analyzed using a bead-based multiplex assay. Carnosine supplementation decreased serum resistin concentrations compared to placebo (mean change from baseline: −35 ± 83 carnosine vs. 35 ± 55 ng/mL placebo, p = 0.04). There was a trend for a reduction in serum leptin concentrations after carnosine supplementation (−76 ± 165 ng/mL carnosine vs. 20 ± 28 ng/mL placebo, p = 0.06). The changes in leptin and resistin concentrations were inversely related to the change in concentration for urinary carnosine (r = −0.72, p = 0.0002; r = −0.67, p = 0.0009, respectively), carnosine-propanal (r = −0.56, p = 0.005; r = −0.63, p = 0.001, respectively) and carnosine-propanol (r = −0.61, p = 0.002; r = −0.60, p = 0.002, respectively). There were no differences between groups in change in adipsin concentrations. Our findings show carnosine supplementation may normalize some, but not all, of the serum adipokine concentrations involved in glucose metabolism, in overweight and obese individuals. Further clinical trials with larger samples are needed to confirm these results.

Variability in quantitative analysis of atherosclerotic plaque inflammation using 18F-FDG PET/CT

BACKGROUND

18F-FDG-PET(/CT) is increasingly used in studies aiming at quantifying atherosclerotic plaque inflammation. Considerable methodological variability exists. The effect of data acquisition and image analysis parameters on quantitative uptake measures, such as standardized uptake value (SUV) and target-to-background ratio (TBR) has not been investigated extensively.

OBJECTIVE

The goal of this study was to explore the effect of several data acquisition and image analysis parameters on quantification of vascular wall 18F-FDG uptake measures, in order to increase awareness of potential variability.

METHODS

Three whole-body emission scans and a low-dose CT scan were acquired 38, 60 and 90 minutes after injection of 18F-FDG in six rheumatoid arthritis patients with high cardiovascular risk profiles.Data acquisition (1 and 2) and image analysis (3, 4 and 5) parameters comprised:1. 18F-FDG uptake time, 2. SUV normalisation, 3. drawing regions/volumes of interest (ROI's/VOI's) according to: a. hot-spot (HS), b. whole-segment (WS) and c. most-diseased segment (MDS), 4. Background activity, 5. Image matrix/voxel size.Intraclass correlation coefficients (ICC's) and Bland Altman plots were used to assess agreement between these techniques and between observers. A linear mixed model was used to determine the association between uptake time and continuous outcome variables.

RESULTS

1. Significantly higher TBRmax values were found at 90 minutes (1,57 95%CI 1,35-1,80) compared to 38 minutes (1,30 95%CI 1,21-1,39) (P = 0,024) 2. Normalising SUV for BW, LBM and BSA significantly influences average SUVmax (2,25 (±0,60) vs 1,67 (±0,37) vs 0,058 (±0,013)). 3. Intraclass correlation coefficients were high in all vascular segments when SUVmax HS was compared to SUVmax WS. SUVmax HS was consistently higher than SUVmax MDS in all vascular segments. 4. Blood pool activity significantly decreases in all (venous and arterial) segments over time, but does not differ between segments. 5. Image matrix/voxel size does not influence SUVmax.

CONCLUSION

Quantitative measures of vascular wall 18F-FDG uptake are affected mainly by changes in data acquisition parameters. Standardization of methodology needs to be considered when studying atherosclerosis and/or vasculitis.

Association between vascular inflammation and non-alcoholic fatty liver disease: Analysis by 18F-fluorodeoxyglucose positron emission tomography

BACKGROUND

Growing evidence suggests that non-alcoholic fatty liver disease (NAFLD) is associated with cardiovascular disease as well as metabolic syndrome. FDG-PET is a novel imaging technique that detects vascular inflammation, which may reflect rupture-prone vulnerable atherosclerotic plaques.

METHODS

Vascular inflammation was measured as the maximum target-to-background ratio (maxTBR), along with various cardiometabolic risk factors in 51 subjects with NAFLD, and compared with 100 age- and gender-matched subjects without NAFLD. The liver attenuation index (LAI), which was measured using computed tomography, was used as a parameter for the diagnosis of NAFLD.

RESULTS

After adjusting for age and sex, both maxTBR and LAI values were associated with several cardiometabolic risk parameters. Furthermore, there was a significant inter-relationship between LAI and maxTBR values (r=-0.227, P=0.005). Individuals with NAFLD had higher maxTBR values than those without NAFLD (P=0.026), although their carotid intima-media thickness (CIMT) values did not differ. The proportion of subjects with NAFLD showed a step-wise increment following the tertiles of maxTBR values (P for trend=0.015). In multiple logistic regression analysis, maxTBR tertiles were independently associated with NAFLD after adjusting for age, gender, systolic blood pressure, triglycerides, HDL-cholesterol, glucose, BUN, creatinine and homeostasis model assessment of insulin resistance (HOMA-IR) (P=0.030). However, their relationship was attenuated after further adjustment for waist circumference or high sensitive C-reactive protein.

CONCLUSION

Patients with NAFLD have an increased risk for vascular inflammation as measured via FDG-PET/CT even without difference in CIMT. (Clinical trials No. NCT01958411, http://www.clinicaltrials.gov/).

The Impact of Organokines on Insulin Resistance, Inflammation, and Atherosclerosis

Immoderate energy intake, a sedentary lifestyle, and aging have contributed to the increased prevalence of obesity, sarcopenia, metabolic syndrome, type 2 diabetes, and cardiovascular disease. There is an urgent need for the development of novel pharmacological interventions that can target excessive fat accumulation and decreased muscle mass and/or strength. Adipokines, bioactive molecules derived from adipose tissue, are involved in the regulation of appetite and satiety, inflammation, energy expenditure, insulin resistance and secretion, glucose and lipid metabolism, and atherosclerosis. Recently, there is emerging evidence that skeletal muscle and the liver also function as endocrine organs that secrete myokines and hepatokines, respectively. Novel discoveries and research into these organokines (adipokines, myokines, and hepatokines) may lead to the development of promising biomarkers and therapeutics for cardiometabolic disease. In this review, I summarize recent data on these organokines and focus on the role of adipokines, myokines, and hepatokines in the regulation of insulin resistance, inflammation, and atherosclerosis.

Relation of resistin to proprotein convertase subtilisin-kexin type 9 levels in coronary artery disease patients with different nutritional status

OBJECTIVE

To investigate the association of resistin with proprotein convertase subtilisin-kexin type 9 (PCSK9) levels, another novel regulator of atherosclerosis, in the condition of coronary artery disease (CAD).

RESEARCH DESIGN AND METHODS

We prospectively enrolled a total of 356 consecutive stable CAD patients who were not treated with lipid-lowering drugs in the present study. The baseline clinical characteristics were collected. Plasma PCSK9 and resistin levels were determined by ELISA. The relationship between plasma PCSK9 and resistin levels was investigated.

RESULTS

Overall, plasma resistin exhibited a positive nonparametric correlation with PCSK9 levels (r = 0.123, p = 0.02). When the patients were classified into groups based on body mass index (BMI), the resistin correlated significantly to the PCSK9 levels in patients with BMI < 25 kg/m(2) (r = 0.162, p = 0.026) but not in patients with BMI ≥ 25 kg/m(2) (r = 0.087, p = 0.205). Multivariate regression analysis corroborated the relation between the PCSK9 and an elevated resistin level in patients with BMI < 25 kg/m(2) independently of traditional parameters including age, sex, BMI, smoking, family history of CAD, systolic blood pressure, glucose, low density lipoprotein cholesterol, white blood cell, neutrophil to lymphocyte ratio, and high-sensitive C-reactive protein.

CONCLUSIONS

Plasma resistin was positively related to PCSK9 levels in CAD patients with normal weight, suggesting that the circulating resistin might represent a link with PCSK9 level variations in CAD progression of normal body weight.

Implications of Pericardial, Visceral and Subcutaneous Adipose Tissue on Vascular Inflammation Measured Using 18FDG-PET/CT

Objective

Pericardial adipose tissue (PAT) is associated with adverse cardiometabolic risk factors and cardiovascular disease (CVD). However, the relative implications of PAT, abdominal visceral and subcutaneous adipose tissue on vascular inflammation have not been explored.

Method and Results

We compared the association of PAT, abdominal visceral fat area (VFA), and subcutaneous fat area (SFA) with vascular inflammation, represented as the target-to-background ratio (TBR), the blood-normalized standardized uptake value measured using ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography (¹⁸FDG-PET) in 93 men and women without diabetes or CVD. Age- and sex-adjusted correlation analysis showed that PAT, VFA, and SFA were positively associated with most cardiometabolic risk factors, including systolic blood pressure, LDL-cholesterol, triglycerides, glucose, insulin resistance and high sensitive C-reactive proteins (hsCRP), whereas they were negatively associated with HDL-cholesterol. In particular, the maximum TBR (maxTBR) values were positively correlated with PAT and VFA (r = 0.48 and r = 0.45, respectively; both P <0.001), whereas SFA showed a relatively weak positive relationship with maxTBR level (r = 0.31, P = 0.003).

Conclusion

This study demonstrated that both PAT and VFA are significantly and similarly associated with vascular inflammation and various cardiometabolic risk profiles.

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.

Obesity and atherosclerosis: mechanistic insights

Obesity is a multifactorial chronic disease characterized by an accumulation of visceral and subcutaneous fat, which leads to a predisposition toward cardiometabolic diseases. A plethora of mechanisms, including abnormalities in lipid metabolism, insulin resistance, inflammation, endothelial dysfunction, adipokine imbalance, and inflammasome activation have been suggested to underlie the relationship between obesity and atherosclerosis. More recent data point toward an emerging role of impaired autophagy and altered gut microbiome homeostasis as potentially contributing factors. This review provides an overview of this area.

Imaging of atherosclerotic plaques in obesity: excessive fat accumulation, plaque progression and vulnerability

Obesity is becoming a major health issue in the world due to sedentary lifestyles and increasing intake of Western diets. Obesity is associated with metabolic abnormalities and atherosclerotic cardiovascular diseases. Adipose tissue has been increasingly considered to play a critical role in inducing metabolic disturbances and promoting atherogenesis. Arterial wall imaging permits direct visualization of atheroma burden in various vascular beds. In addition, recent advances in imaging technology help characterize components, microstructures and functional features of atherosclerotic plaques. These imaging modalities have contributed to elucidating factors associated with atherosclerosis in obese patients. Also, it provides opportunities to evaluate the effect of novel therapies on plaques in the setting of obesity. The findings of recent imaging studies and the clinical implications will be reviewed.

Adipokines as a novel link between obesity and atherosclerosis

The traditional perception of adipose tissue as a storage organ of fatty acids has been replaced by the notion that adipose tissue is an active endocrine organ, releasing various adipokines that are involved in the pathogenesis of obesity-related metabolic disturbances. Obesity is a well-known risk factor for atherosclerosis, and accelerates atherosclerosis by many mechanisms such as increase in blood pressure and glucose level, abnormal lipid profiles, and systemic inflammation. Furthermore, growing evidence suggests that some adipokines directly mediate the process of atherosclerosis by influencing the function of endothelial cells, arterial smooth muscle cells, and macrophages in vessel walls. In obese patients, the secretion and coordination of such adipokines is abnormal, and the secretion of specific adipokines increases or decreases. Accordingly, the discovery of new adipokines and elucidation of their functions might lead to a new treatment strategy for metabolic disorders related to obesity, including cardiovascular diseases.

Subclinical vascular inflammation in subjects with normal weight obesity and its association with body fat: an 18 F-FDG-PET/CT study

Background

Although body mass index (BMI) is the most widely accepted parameter for defining obesity, recent studies have indicated a unique set of patients who exhibit normal BMI and excess body fat (BF), which is termed as normal weight obesity (NWO). Increased BF is an established risk factor for atherosclerosis. However, it is unclear whether NWO subjects already have a higher degree of vascular inflammation compared to normal weight lean (NWL) subjects; moreover, the association of BF with vascular inflammation in normal weight subjects is largely unknown.

Methods

NWO and NWL subjects (n = 82 in each group) without any history of significant vascular disease were identified from a 3-year database of consecutively recruited patients undergoing ¹⁸ F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸ F-FDG-PET/CT) at a self-referred Healthcare Promotion Program. The degree of subclinical vascular inflammation was evaluated using the mean and maximum target-to-background ratios (TBRmean and TBRmax) of the carotid artery, which were measured by ¹⁸ F-FDG-PET/CT (a noninvasive tool for assessing vascular inflammation).

Results

We found that metabolically dysregulation was greater in NWO subjects than in NWL subjects, with a significantly higher blood pressure, higher fasting glucose level, and worse lipid profile. Moreover, NWO subjects exhibited higher TBR than NWL subjects (TBRmean: 1.33 ± 0.16 versus 1.45 ± 0.19, p < 0.001; TBRmax: 1.52 ± 0.23 versus 1.67 ± 0.25, p < 0.001). TBR was significantly associated with total BF (TBRmean: r = 0.267, p = 0.001; TBRmax: r = 0.289, p < 0.001), age (TBRmean: r = 0.170, p = 0.029; TBRmax: r = 0.165, p = 0.035), BMI (TBRmean: r = 0.184, p = 0.018; TBRmax: r = 0.206, p = 0.008), and fasting glucose level (TBRmean: r = 0.157, p = 0.044; TBRmax: r = 0.182, p = 0.020). In multiple linear regression analysis, BF was an independent determinant of TBRmean and TBRmax, after adjusting for age, BMI, and fasting glucose level (TBRmean: regression coefficient = 0.020, p = 0.008; TBRmax: regression coefficient = 0.028, p = 0.005). Compared to NWL, NWO was also independently associated with elevated TBRmax values, after adjusting for confounding factors (odds ratio = 2.887, 95% confidence interval 1.206–6.914, p = 0.017).

Conclusions

NWO is associated with a higher degree of subclinical vascular inflammation, of which BF is a major contributing factor. These results warrant investigations for subclinical atherosclerosis in NWO patients.

Adipose tissue as an endocrine organ

Obesity is one of the most important health challenges faced by developed countries and is increasingly affecting adolescents and children. Obesity is also a considerable risk factor for the development of numerous other chronic diseases, such as insulin resistance, type 2 diabetes, heart disease and nonalcoholic fatty liver disease. The epidemic proportions of obesity and its numerous comorbidities are bringing into focus the highly complex and metabolically active adipose tissue. Adipose tissue is increasingly being considered as a functional endocrine organ. This article discusses the endocrine effects of adipose tissue during obesity and the systemic impact of this signaling.

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.

The influence of sodium- and calcium-regulatory hormone interventions on adipocytokines in obesity and diabetes

OBJECTIVE

The renin-angiotensin-aldosterone system (RAAS), vitamin D, and parathyroid hormone have all been implicated as regulators of adipocytokines and inflammation. We evaluated human interventional study protocols to investigate whether controlled modulations of these calcium- and sodium-regulatory hormones could influence adipocytokines and inflammation in obesity and diabetes.

METHODS

Post-hoc analyses of two separate human protocols (Protocol 1, n=14; Protocol 2, n=24) conducted in a clinical research setting after rigorous control of diet, posture, medications, and diurnal rhythm, were performed. Protocol 1 evaluated obese hypertensives with vitamin D deficiency who received an infusion of angiotensin II (AngII) before and after 1month of vitamin D3 therapy. Protocol 2 evaluated obese subjects with type 2 diabetes who also received AngII. Adipocytokines and inflammatory markers were measured before and after vitamin D3 therapy, and also before and after infusions of AngII.

RESULTS

Vitamin D3 therapy significantly raised 25(OH)D and 1,25(OH)2D concentrations, and lowered parathyroid hormone, but had no effect on concentrations of adiponectin, resistin, leptin, IL-6, PAI-1, urinary TGFβ1, or HOMA-IR. AngII infusions, despite significant elevations in blood pressure and serum aldosterone, did not influence adipocytokine concentrations in either protocol.

CONCLUSION

In contrast to prior studies conducted in healthy populations, or those that could not control major regulators of the RAAS or adipocytokines, we observed that robust modulations in calcium- and sodium-regulatory hormones did not influence adipocytokines or inflammation in obesity or diabetes. Adipose-tissue physiology in these conditions may alter the hormonal regulation of inflammatory parameters.

Molecular imaging in atherosclerosis: FDG PET

18F-FDG PET is a new noninvasive tool for inflammation functional imaging. Low spatial resolution is now compensated by coregistration with CT or MRI. New mechanistic insights have emerged from animal and histology to explain the obtained signals by hypoxia, macrophage infiltration, and differentiation. Mixed results have been found in biomarkers studies. Interesting data have come recently linking plaque anatomy and function in carotids and in aortic aneurysms as well as inflammation and events. In coronary arteries, plaque assessment is still hampered by myocardium uptake but developments are being made. 18-FDG PET has been able to monitor inflammation before and after several therapies in animals and humans but to date the lack of standardization and the absence of prospective event-driven studies prevent this promising technique to be used in clinical practice.

Association of serum resistin levels with metabolic syndrome and early atherosclerosis in obese Chinese children

AIM

To investigate the association of serum resistin levels with metabolic syndrome (MS) and early atherosclerosis in obese children.

METHODS

A total of 176 obese children and 88 healthy children were enrolled in this study, and were gender and age matched. Obesity was defined as a body mass index (BMI) of ≥ the 95th percentile for age and sex. All children had a physical examination and routine hematology testing for fasting blood glucose, insulin, and lipids profile. Homeostasis model of assessment of insulin resistance (HOMA-IR) was calculated, as insulin resistance has a central role in the pathophysiology of MS. Non-invasive ultrasound measurement was obtained to investigate carotid intima-media thickness (IMT) as the markers of early atherosclerosis. Path analysis was used to evaluate the value of resistin levels to early atherosclerosis.

RESULTS

The resistin levels were higher in obese children compared to healthy children (23.14 ± 7.35 vs. 17.1 ± 5.7 ng/mL, p<0.05), and it is positively correlated with BMI, waist circumference, systolic blood pressure, fasting insulin, HOMA-IR, IMT and high sensitive CRP (Hs-CRP), but not related to diastolic blood pressure, blood lipids and fasting glucose. A positive linear correlation was observed between resistin and the number of MS components. Path analysis indicated serum resistin can directly (β=0.304, p=0.001), and indirectly via HOMA-IR (β=0.085, p=0.008) and Hs-CRP (β=0.047, p=0.029), contribute to early atherosclerosis.

CONCLUSION

Resistin not only play a certain role in the presence of MS, but also indirectly via insulin resistance and Hs-CRP to contribute to early atherosclerosis in obese children.

Adipocytokine levels mark endothelial function in normotensive individuals

Background

Endothelial dysfunction is an independent risk factor for cardiovascular events. Inflammatory mediators released by the adipose tissue can lead to local insulin resistance and endothelial dysfunction. This study addressed the relationship of adipocytokines with endothelial function and blood pressure.

Methods

In 92 newly diagnosed, drug-naïve essential hypertensive patients (HT, mean age 49 yrs) without organ damage and 66 normotensive subjects (NT, mean age 47 yrs), by an automated system, we measured endothelium-dependent and -independent vasodilation as brachial artery flow-mediated dilation before and after administration of glyceryl-trinitrate. Retinol binding protein-4 (RBP4) and resistin levels were determined by ELISA and RIA, respectively. Oxidative stress was evaluated by measuring serum malondyaldehyde (MDA).

Results

Flow-mediated dilation was significantly (p = 0.03) lower in HT (5.3 ± 2.6%) than NT (6.1 ± 3.1%), while response to glyceryl-trinitrate (7.5 ± 3.7% vs 7.9 ± 3.4%) was similar. RBP4 (60.6 ± 25.1 vs 61.3 ± 25.9 μg/ml), resistin (18.8 ± 5.3 vs 19.9 ± 6.1 ng/ml) and MDA levels (2.39 ± 1.26 vs 2.08 ± 1.17 nmol/ml) were not different in HT and NT.

RBP4 (r = −0.25; p = 0.04) and resistin levels (r = −0.29; p = 0.03) were related to flow-mediated dilation in NT, but not in HT (r = −0.03 and r = −0.10, respectively). In NT, multivariate analysis including RBP4 and confounders showed that only BMI or waist circumference remained related to flow- mediated dilation. In the multivariate model including resistin and confounders, BMI, age and resistin were significantly related to flow-mediated dilation, while only age significant correlated with this parameter when BMI was replaced by waist circumference.

Conclusions

Adipocytokine levels may be independent predictors of endothelial dysfunction in the peripheral circulation of healthy subjects, providing a pathophysiological link between inflammation from adipose tissue and early vascular alterations.

Pro- and antiatherogenic effects of a dominant-negative P465L mutation of peroxisome proliferator-activated receptor-γ in apolipoprotein E-Null mice

OBJECTIVE

The dominant-negative mutation, P467L, in peroxisome proliferator-activated receptor-γ (PPARγ) affects adipose tissue distribution, insulin sensitivity, and blood pressure in heterozygous humans. We hypothesized that the equivalent mutation, PPARγ-P465L, in mice will worsen atherosclerosis.

METHODS AND RESULTS

Apolipoprotein E-null mice with and without PPARγ-P465L mutation were bred in 129S6 inbred genetic background. Mild hypertension and lipodystrophy of PPARγ-P465L persisted in the apolipoprotein E-null background. Glucose homeostasis was normal, but plasma adiponectin was significantly lower and resistin was higher in PPARγ-P465L mice. Plasma cholesterol and lipoprotein distribution were not different, but plasma triglycerides tended to be reduced. Surprisingly, there were no overall changes in the atherosclerotic plaque size or composition. PPARγ-P465L macrophages had a small decrease in CD36 mRNA and a small yet significant reduction in very-low-density lipoprotein uptake in culture. In unloaded apolipoprotein E-null macrophages with PPARγ-P465L, cholesterol uptake was reduced whereas apolipoprotein AI-mediated efflux was increased. However, when cells were cholesterol loaded in the presence of acetylated low-density lipoprotein, no genotype difference in uptake or efflux was apparent. A reduction of vascular cell adhesion molecule-1 expression in aorta suggests a relatively antiatherogenic vascular environment in mice with PPARγ-P465L.

CONCLUSIONS

Small, competing pro- and antiatherogenic effects of PPARγ-P465L mutation result in unchanged plaque development in apolipoprotein E-deficient mice.

Circulating levels of resistin, IL-6 and lipid profile in elderly patients with ischemic heart disease with and without diabetes

Background: The cytokines that act as inflammatory hormones show a role in coronary atherosclerotic disease. Aims: This study aimed to measure serum resistin, IL-6 levels and lipid profile in nondiabetic controls, diabetics, and ischemic heart disease subjects with and without diabetes. Association between resistin and IL-6 was also determined. Materials & methods: In this comparative cross-sectional study, 147 subjects were selected, aged between 40 and 70 years. Subjects were divided into four groups as mentioned above. Plasma glucose was measured using the gluco-oxidase method. Lipid profile levels were measured using standard enzymatic methods. Levels of resistin and IL-6 were determined by ELISA. Results: Out of 147 patients, 36 were controls and 111 were cases. Serum resistin and IL-6 levels increased significantly in diabetics (23.4 ± 0.74 ng/ml and 73.1 ± 2.57 ng/ml, respectively) and nondiabetics with ischemic heart disease (14.1 ± 0.51 ng/ml and 66.2 ± 2.08 ng/ml, respectively) compared with diabetics and nondiabetic controls. Positive correlations were found between IL-6 and resistin, and a significant positive correlation was shown in ischemic heart disease groups (r = 0.659; p = 0.001). Conclusion: This study shows that the plasma resistin and IL-6 concentrations increased significantly in patients with ischemic heart disease with and without diabetes. This shows that there is a possible role of resistin and IL-6 in inflammatory processes, especially in atherosclerosis.

The effects of 3-month atorvastatin therapy on arterial inflammation, calcification, abdominal adipose tissue and circulating biomarkers

PURPOSE

(18)F-Fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT has the potential to track vascular inflammation and monitor therapeutic response. The purpose of this study was to determine the association between arterial inflammation, calcification and serological biomarkers in subjects with atherosclerosis, and to assess their therapeutic response to 12-week atorvastatin treatment.

METHODS

Forty-three statin-naïve subjects with atherosclerosis received atorvastatin (40 mg/day) for 12 weeks and underwent (18)F-FDG PET/CT, coronary calcification and abdominal adipose tissue volume measurements. A panel of serological biomarkers was analysed. Arterial inflammation was measured at seven arterial segments and normalized to venous FDG activity to produce target to background ratios (TBR). Thirty-four subjects without cardiovascular disease who repeated PET 1-4 years apart for routine health check-ups were retrospectively evaluated for comparison.

RESULTS

The baseline mean TBR values in atherosclerotic patients were positively correlated with age (R = 0.36), body mass index (R = 0.54), abdominal visceral adipose tissue volume (R = 0.65), coronary calcification score (R = 0.40), levels of low-density lipoprotein cholesterol (R = 0.54), matrix metalloproteinase (MMP)-9 (R = 0.46) and fatty acid binding protein 4 (FABP4) (R = 0.67, all p < 0.05). The TBR as well as high-sensitivity C-reactive protein (hsCRP), E-selectin, MMP-9, monocyte chemotactic protein 1, FABP4 and follistatin values were reduced significantly after the 12-week atorvastatin treatment. The TBR reduction marginally correlated with changes in MMP-9 levels (R = 0.56, p = 0.05). The control group, whose median age was younger, by comparison had lower hsCRP and arterial TBR than the subjects with atherosclerosis (all p < 0.05), and moreover had a slight but insignificant increase in mean TBR at their 2.5±0.8 year follow-up.

CONCLUSION

The medium dose of atorvastatin over a 12-week period resulted in a significant reduction of arterial inflammation as well as various circulating biomarkers.

Association of circulating omentin-1 level with arterial stiffness and carotid plaque in type 2 diabetes

BACKGROUND

Adipokines contribute directly to the atherosclerotic process, connecting metabolic disorders such as obesity and diabetes to cardiovascular disease. Omentin-1 is a recently discovered novel adipokine, so data about the relationship of this adipokine to vascular health in type 2 diabetes is limited.

METHODS

We enrolled 60 people with type 2 diabetes, with or without carotid plaque, and 30 participants with normal glucose tolerance. We measured serum omentin-1, high-sensitivity C-reactive protein (hsCRP) levels, and the homeostasis model assessment of insulin resistance (HOMA-IR), as well as other cardiovascular risk factors. Vascular health was assessed by brachial ankle pulse wave velocity (baPWV) and carotid intima-media thickness (IMT).

RESULTS

Serum omentin-1 levels were significantly decreased in type 2 diabetes patients compared to normal glucose controls and was further reduced in type 2 diabetes patients with carotid plaque compared to those without carotid plaque. Multiple stepwise regression analysis showed that age, systolic blood pressure, history of use of statins, angiotensin receptor blockers or angiotensin-converting enzyme inhibitors, and serum omentin-1 level were independent factors determining baPWV in people with type 2 diabetes (r2 = 0.637). Furthermore, in multivariate logistic regression analysis, circulating omentin-1 level was an independent decisive factor for the presence of carotid plaque in type 2 diabetes patients, even after adjusting for age, gender, body mass index, systolic blood pressure, fasting blood glucose, low density lipoprotein cholesterol, and history of smoking and medication (odds ratio, 0.621; 95% confidence interval, 0.420-0.919; P = 0.017).

CONCLUSIONS

Circulating omentin-1 level was independently correlated with arterial stiffness and carotid plaque in type 2 diabetes, even after adjusting for other cardiovascular risk factors and detailed medication history.

Circulating chemerin level is independently correlated with arterial stiffness

AIM

Adipokines have been implicated in the pathogenesis of obesity and obesity-related disorders, including atherosclerosis. Chemerin is a recently discovered adipokine which is closely correlated with various metabolic phenotypes in humans. We examined the association between circulating chemerin levels and arterial stiffness, as represented by the brachial ankle pulse wave velocity (baPWV).

METHODS

Fifty-eight obese and 62 non-obese individuals participated in the study. We measured the serum chemerin and high sensitivity C-reactive protein (hsCRP) levels, and the homeostasis model assessment of insulin resistance (HOMA-IR), as well as other cardiovascular risk factors. Vascular health was assessed by the baPWV and carotid intima-media thickness (IMT).

RESULTS

The serum chemerin level was significantly increased in obese individuals compared with lean controls (120.14±19.43 ng/mL vs. 106.81±23.39 ng/mL, p = 0.001). The circulating chemerin level had a significant positive correlation with the body mass index, waist circumference, HOMA-IR, and low-density lipoprotein-cholesterol, triglycerides, and hsCRP levels. The serum chemerin level was significantly associated with the baPWV (r= 0.280, p= 0.002), but not the carotid IMT (r= 0.065, p= 0.504). Multiple stepwise regression analysis showed that age (p < 0.001), waist circumference (p= 0.038), systolic blood pressure (p < 0.001), and serum fasting glucose (p= 0.003) and chemerin levels (p= 0.017) were definitive risk factors for arterial stiffness (r(2)=0.457).

CONCLUSIONS

The circulating chemerin level was an independent risk factor for arterial stiffness even after adjusting for other cardiovascular risk factors.

Association between sRAGE, esRAGE levels and vascular inflammation: analysis with (18)F-fluorodeoxyglucose positron emission tomography

BACKGROUND

The receptor for advanced glycation end-products (RAGE) and its diverse ligands play a pivotal role in the development of cardiovascular disease. Soluble forms of RAGE (sRAGE), including the splice variant endogenous secretory RAGE (esRAGE), may neutralize AGE-RAGE mediated vascular damage by acting as a decoy. (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a novel imaging technique for detecting vascular inflammation.

METHODS

We examined vascular inflammation measured using FDG-PET in 41 type 2 diabetes patients and 41 healthy control subjects in the right carotid artery. Vascular (18)F-FDG uptake was measured as the blood-normalized standardized uptake value (SUV), known as the target-to-background ratio (TBR). In addition, their relationship with carotid intima-media thickness (CIMT), estimated GFR (eGFR), and other cardiovascular risk factors was evaluated.

RESULTS

Both mean and maximum TBR values were significantly higher in patients with type 2 diabetes compared to healthy subjects. After adjusting for age and gender, sRAGE levels were significantly correlated with both mean and maximum TBR values, but not with CIMT values. Multiple linear regression analysis showed that maximum TBR values were independently associated with sRAGE levels in addition to HbA1c and eGFR.

CONCLUSIONS

Circulating sRAGE showed significant association with TBR values measured using FDG-PET, which reflect vascular inflammation.

Similarity of mouse perivascular and brown adipose tissues and their resistance to diet-induced inflammation

Thoracic perivascular adipose tissue (PVAT) is a unique adipose depot that likely influences vascular function and susceptibility to pathogenesis in obesity and the metabolic syndrome. Surprisingly, PVAT has been reported to share characteristics of both brown and white adipose, but a detailed direct comparison to interscapular brown adipose tissue (BAT) has not been performed. Here we show by full genome DNA microarray analysis that global gene expression profiles of PVAT are virtually identical to BAT, with equally high expression of Ucp-1, Cidea, and other genes known to be uniquely or very highly expressed in BAT. PVAT and BAT also displayed nearly identical phenotypes upon immunohistochemical analysis, and electron microscopy confirmed that PVAT contained multilocular lipid droplets and abundant mitochondria. Compared with white adipose tissue (WAT), PVAT and BAT from C57BL6/J mice fed a high-fat diet for 13 wk had markedly lower expression of immune cell-enriched mRNAs, suggesting resistance to obesity-induced inflammation. Indeed, staining of BAT and PVAT for macrophage markers (F4/80 and CD68) in obese mice showed virtually no macrophage infiltration, and FACS analysis of BAT confirmed the presence of very few CD11b(+)/CD11c(+) macrophages in BAT (1.0%) compared with WAT (31%). In summary, murine PVAT from the thoracic aorta is virtually identical to interscapular BAT, is resistant to diet-induced macrophage infiltration, and thus may play an important role in protecting the vascular bed from inflammatory stress.

Novel adiponectin-resistin (AR) and insulin resistance (IRAR) indexes are useful integrated diagnostic biomarkers for insulin resistance, type 2 diabetes and metabolic syndrome: a case control study

Background

Adiponectin and resistin are adipokines which modulate insulin action, energy, glucose and lipid homeostasis. Meta-analyses showed that hypoadiponectinemia and hyperresistinemia are strongly associated with increased risk of insulin resistance, type 2 diabetes (T2DM), metabolic syndrome (MS) and cardiovascular disease. The aim of this study was to propose a novel adiponectin-resistin (AR) index by taking into account both adiponectin and resistin levels to povide a better indicator of the metabolic homeostasis and metabolic disorders. In addition, a novel insulin resistance (IR_AR) index was proposed by integration of the AR index into an existing insulin resistance index to provide an improved diagnostic biomarker of insulin sensitivity.

Methods

In this case control study, anthropometric clinical and metabolic parameters including fasting serum total adiponectin and resistin levels were determined in 809 Malaysian men (208 controls, 174 MS without T2DM, 171 T2DM without MS, 256 T2DM with MS) whose ages ranged between 40-70 years old. Significant differences in continuous variables among subject groups were confirmed by ANCOVA or MANCOVA test using 1,000 stratified bootstrap samples with bias corrected and accelerated (BCa) 95% CI. Spearman's rho rank correlation test was used to test the correlation between two variables.

Results

The AR index was formulated as 1+log₁₀(R₀)-log₁₀(A₀). The AR index was more strongly associated with increased risk of T2DM and MS than hypoadiponectinemia and hyperresistinemia alone. The AR index was more strongly correlated with the insulin resistance indexes and key metabolic endpoints of T2DM and MS than adiponectin and resistin levels alone. The AR index was also correlated with a higher number of MS components than adiponectin and resistin levels alone. The IR_AR index was formulated as log₁₀(I₀G₀)+log₁₀(I₀G₀)log₁₀(R₀/A₀). The normal reference range of the IR_AR index for insulin sensitive individuals was between 3.265 and 3.538. The minimum cut-off values of the IR_AR index for insulin resistance assessment were between 3.538 and 3.955.

Conclusions

The novel AR and IR_AR indexes are cost-effective, precise, reproducible and reliable integrated diagnostic biomarkers of insulin sensitivity for screening subjects with increased risk of future development of T2DM and MS.