Evidence of a causal relationship between high serum adiponectin levels and increased cardiovascular mortality rate in patients with type 2 diabetes

Adiponectin Reduces Glomerular Endothelial Glycocalyx Disruption and Restores Glomerular Barrier Function in a Mouse Model of Type 2 Diabetes

Adiponectin has vascular anti-inflammatory and protective effects. Although adiponectin protects against the development of albuminuria, historically, the focus has been on podocyte protection within the glomerular filtration barrier (GFB). The first barrier to albumin in the GFB is the endothelial glycocalyx (eGlx), a surface gel-like barrier covering glomerular endothelial cells (GEnCs). In diabetes, eGlx dysfunction occurs before podocyte damage; hence, we hypothesized that adiponectin could protect from eGlx damage to prevent early vascular damage in diabetic kidney disease (DKD). Globular adiponectin (gAd) activated AMPK signaling in human GEnCs through AdipoR1. It significantly reduced eGlx shedding and the tumor necrosis factor-α (TNF-α)-mediated increase in syndecan-4 (SDC4) and MMP2 mRNA expression in GEnCs in vitro. It protected against increased TNF-α mRNA expression in glomeruli isolated from db/db mice and against expression of genes associated with glycocalyx shedding (namely, SDC4, MMP2, and MMP9). In addition, gAd protected against increased glomerular albumin permeability (Ps'alb) in glomeruli isolated from db/db mice when administered intraperitoneally and when applied directly to glomeruli (ex vivo). Ps'alb was inversely correlated with eGlx depth in vivo. In summary, adiponectin restored eGlx depth, which was correlated with improved glomerular barrier function, in diabetes.

ARTICLE HIGHLIGHTS

Precision prognostics for cardiovascular disease in Type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Precision medicine has the potential to improve cardiovascular disease (CVD) risk prediction in individuals with Type 2 diabetes (T2D).

METHODS

We conducted a systematic review and meta-analysis of longitudinal studies to identify potentially novel prognostic factors that may improve CVD risk prediction in T2D. Out of 9380 studies identified, 416 studies met inclusion criteria. Outcomes were reported for 321 biomarker studies, 48 genetic marker studies, and 47 risk score/model studies.

RESULTS

Out of all evaluated biomarkers, only 13 showed improvement in prediction performance. Results of pooled meta-analyses, non-pooled analyses, and assessments of improvement in prediction performance and risk of bias, yielded the highest predictive utility for N-terminal pro b-type natriuretic peptide (NT-proBNP) (high-evidence), troponin-T (TnT) (moderate-evidence), triglyceride-glucose (TyG) index (moderate-evidence), Genetic Risk Score for Coronary Heart Disease (GRS-CHD) (moderate-evidence); moderate predictive utility for coronary computed tomography angiography (low-evidence), single-photon emission computed tomography (low-evidence), pulse wave velocity (moderate-evidence); and low predictive utility for C-reactive protein (moderate-evidence), coronary artery calcium score (low-evidence), galectin-3 (low-evidence), troponin-I (low-evidence), carotid plaque (low-evidence), and growth differentiation factor-15 (low-evidence). Risk scores showed modest discrimination, with lower performance in populations different from the original development cohort.

CONCLUSIONS

Despite high interest in this topic, very few studies conducted rigorous analyses to demonstrate incremental predictive utility beyond established CVD risk factors for T2D. The most promising markers identified were NT-proBNP, TnT, TyG and GRS-CHD, with the highest strength of evidence for NT-proBNP. Further research is needed to determine their clinical utility in risk stratification and management of CVD in T2D.

A cross-ancestry genome-wide meta-analysis, fine-mapping, and gene prioritization approach to characterize the genetic architecture of adiponectin

Previous genome-wide association studies (GWASs) for adiponectin, a complex trait linked to type 2 diabetes and obesity, identified >20 associated loci. However, most loci were identified in populations of European ancestry, and many of the target genes underlying the associations remain unknown. We conducted a cross-ancestry adiponectin GWAS meta-analysis in ≤46,434 individuals from the Metabolic Syndrome in Men (METSIM) cohort and the ADIPOGen and AGEN consortiums. We combined study-specific association summary statistics using a fixed-effects, inverse variance-weighted approach. We identified 22 loci associated with adiponectin (p < 5×10-8), including 15 known and seven previously unreported loci. Among individuals of European ancestry, Genome-wide Complex Traits Analysis joint conditional analysis (GCTA-COJO) identified 14 additional distinct signals at the ADIPOQ, CDH13, HCAR1, and ZNF664 loci. Leveraging the cross-ancestry data, FINEMAP + SuSiE identified 45 causal variants (PP > 0.9), which also exhibited potential pleiotropy for cardiometabolic traits. To prioritize target genes at associated loci, we propose a combinatorial likelihood scoring formalism (Gene Priority Score [GPScore]) based on measures derived from 11 gene prioritization strategies and the physical distance to the transcription start site. With GPScore, we prioritize the 30 most probable target genes underlying the adiponectin-associated variants in the cross-ancestry analysis, including well-known causal genes (e.g., ADIPOQ, CDH13) and additional genes (e.g., CSF1, RGS17). Functional association networks revealed complex interactions of prioritized genes, their functionally connected genes, and their underlying pathways centered around insulin and adiponectin signaling, indicating an essential role in regulating energy balance in the body, inflammation, coagulation, fibrinolysis, insulin resistance, and diabetes. Overall, our analyses identify and characterize adiponectin association signals and inform experimental interrogation of target genes for adiponectin.

Inter-organ crosstalk during development and progression of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is characterized by tissue-specific insulin resistance and pancreatic β-cell dysfunction, which result from the interplay of local abnormalities within different tissues and systemic dysregulation of tissue crosstalk. The main local mechanisms comprise metabolic (lipid) signalling, altered mitochondrial metabolism with oxidative stress, endoplasmic reticulum stress and local inflammation. While the role of endocrine dysregulation in T2DM pathogenesis is well established, other forms of inter-organ crosstalk deserve closer investigation to better understand the multifactorial transition from normoglycaemia to hyperglycaemia. This narrative Review addresses the impact of certain tissue-specific messenger systems, such as metabolites, peptides and proteins and microRNAs, their secretion patterns and possible alternative transport mechanisms, such as extracellular vesicles (exosomes). The focus is on the effects of these messengers on distant organs during the development of T2DM and progression to its complications. Starting from the adipose tissue as a major organ relevant to T2DM pathophysiology, the discussion is expanded to other key tissues, such as skeletal muscle, liver, the endocrine pancreas and the intestine. Subsequently, this Review also sheds light on the potential of multimarker panels derived from these biomarkers and related multi-omics for the prediction of risk and progression of T2DM, novel diabetes mellitus subtypes and/or endotypes and T2DM-related complications.

Precision Prognostics for Cardiovascular Disease in Type 2 Diabetes: A Systematic Review and Meta-analysis

Background Precision medicine has the potential to improve cardiovascular disease (CVD) risk prediction in individuals with type 2 diabetes (T2D). Methods We conducted a systematic review and meta-analysis of longitudinal studies to identify potentially novel prognostic factors that may improve CVD risk prediction in T2D. Out of 9380 studies identified, 416 studies met inclusion criteria. Outcomes were reported for 321 biomarker studies, 48 genetic marker studies, and 47 risk score/model studies. Results Out of all evaluated biomarkers, only 13 showed improvement in prediction performance. Results of pooled meta-analyses, non-pooled analyses, and assessments of improvement in prediction performance and risk of bias, yielded the highest predictive utility for N-terminal pro b-type natriuretic peptide (NT-proBNP) (high-evidence), troponin-T (TnT) (moderate-evidence), triglyceride-glucose (TyG) index (moderate-evidence), Genetic Risk Score for Coronary Heart Disease (GRS-CHD) (moderate-evidence); moderate predictive utility for coronary computed tomography angiography (low-evidence), single-photon emission computed tomography (low-evidence), pulse wave velocity (moderate-evidence); and low predictive utility for C-reactive protein (moderate-evidence), coronary artery calcium score (low-evidence), galectin-3 (low-evidence), troponin-I (low-evidence), carotid plaque (low-evidence), and growth differentiation factor-15 (low-evidence). Risk scores showed modest discrimination, with lower performance in populations different from the original development cohort. Conclusions Despite high interest in this topic, very few studies conducted rigorous analyses to demonstrate incremental predictive utility beyond established CVD risk factors for T2D. The most promising markers identified were NT-proBNP, TnT, TyG and GRS-CHD, with the highest strength of evidence for NT-proBNP. Further research is needed to determine their clinical utility in risk stratification and management of CVD in T2D.

Adiponectin Levels in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

INTRODUCTION

Adipose tissue plays an important role in the pathogenesis of inflammatory conditions. The role of adipokines in inflammatory bowel disease (IBD) has been evaluated in the current literature with conflicting results. The aim of this study was to evaluate adiponectin levels in IBD patients, including Crohn's disease (CD) and ulcerative colitis (UC), compared to controls, as well as further subgroup analyses. Hence, assessing the potential role of adiponectin as a surrogate marker.

METHODS

We performed a systematic electronic search on PubMed, Embase, Scopus, and Cochrane Library, including observational or interventional studies evaluating serum or plasma adiponectin levels in IBD patients in humans. The primary summary outcome was the mean difference (MD) in serum or plasma adiponectin levels between IBD patients versus controls. Subgroup analyses were conducted involving adiponectin levels in CD and UC compared to controls, as well as CD compared to UC.

RESULTS

A total of 20 studies were included in our qualitative synthesis and 14 studies in our quantitative synthesis, with a total population sample of 2,085 subjects. No significant MD in serum adiponectin levels was observed between IBD patients versus controls {-1.331 (95% confidence interval [CI]: -3.135-0.472)}, UC patients versus controls (-0.213 [95% CI: -1.898-1.472]), and CD patients versus controls (-0.851 [95% CI: -2.263-0.561]). Nevertheless, a significant MD was found between UC patients versus CD patients (0.859 [95% CI: 0.097-1.622]).

CONCLUSIONS

Serum adiponectin levels were not able to differentiate between IBD, UC, and CD patients compared to controls. However, significantly higher serum adiponectin levels were observed in UC compared to CD patients.

Serum adiponectin concentrations as a risk factor for cardiovascular complications in type 1 diabetes

AIM

By analyzing data from DCCT/EDIC study, we investigated the associations of serum adiponectin concentrations with macrovascular complications and cardiovascular events in T1D.

MATERIALS AND METHODS

Adiponectin concentrations were measured in EDIC year 8. The participants (n = 1040) were divided into four groups by quartiles of adiponectin concentrations. The association of macrovascular complications and cardiovascular events were analyzed by using multivariable regression and Cox proportional hazards models.

RESULTS

High adiponectin concentrations were associated with decreased risk of peripheral artery disease represented by ankle brachial index (ORs (95% CI): 0.22 (0.07-0.72), 0.48 (0.18-1.25), and 0.38 (0.14-0.99) in fourth, third, and second quartiles compared with first quartile), with reduced carotid intima-media thickness, and with increased LVEDV index. Moreover, high adiponectin concentrations were also associated with increased risk of any cardiovascular events (HRs (95% CI): 2.59 (1.10-6.06), 2.03 (0.90-4.59), and 1.22 (0.52-2.85)) and major atherosclerotic cardiovascular events (HRs (95% CI): 11.37 (2.04-63.43), 5.68 (1.04-31.07), and 3.76 (0.65-21.77) in fourth, third, and second quartiles compared with first quartile), however, after adjustments with LVEDV index, these associations were diminished.

CONCLUSIONS

Adiponectin may protect carotid atherosclerosis and peripheral artery disease in T1D. It may be associated with increased cardiovascular events, depending on cardiac structural changes.

Mendelian randomization study reveals a causal relationship between adiponectin and LDL cholesterol in Africans

Adiponectin has been associated with cardiometabolic traits in observational studies across populations, yet it is unclear if these associations are causal. We performed Mendelian randomization (MR) analysis to assess the relationship between adiponectin and cardiometabolic traits in sub-Saharan Africans. We constructed a polygenic risk score (PRS) for adiponectin levels across 3354 unrelated sub-Saharan Africans. The PRS was used as the instrumental variable in two-stage least-squares MR analysis to assess its association with insulin resistance, HDL, LDL, total cholesterol, triglycerides, blood pressure, Type 2 Diabetes (T2D), and hypertension. The adiponectin PRS was causally related with LDL (β = 0.55, 95%CI 0.07-1.04, P-value = 0.024) but not the other traits. This association was observed in both overweight/obese and normal weight individuals, but only reached statistical significance among overweight/obese individuals (β = 0.55, 95%CI 0.01-1.08, P-value = 0.045). In normal weight individuals, the adiponectin PRS was associated with T2D (OR = 0.13, 95%CI 0.02-0.73, P-value = 0.021), and in men with HDL (β = 1.03, 95%CI 0.14-1.92, P-value = 0.023). The findings of this first MR study in sub-Saharan Africans support a causal relationship of adiponectin with LDL, with T2D in normal weight individuals only, and with HDL in men only. These observations add to the small but growing literature on adiponectin MR studies.

Genetic variations in adiponectin levels and dietary patterns on metabolic health among children with normal weight versus obesity: the BCAMS study

BACKGROUND/OBJECTIVES

Adiponectin represents an important link between adipose tissue dysfunction and cardiometabolic risk in obesity; however, there is a lack of data on the effects of adiponectin-related genetic variations and gene-diet interactions on metabolic disorders in children. We aimed to investigate possible interactions between adiponectin-related genetic variants and habitual dietary patterns on metabolic health among children with normal weight versus overweight/obesity, and whether these effects in childhood longitudinally contribute to metabolic risk at follow-up.

SUBJECTS/METHODS

In total, 3,317 Chinese children aged 6-18 at baseline and 339 participants at 10-year follow-up from the Beijing Child and Adolescent Metabolic Syndrome study cohort were included. Baseline lifestyle factors, plasma adiponectin levels, and six adiponectin-related genetic variants resulting from GWAS in East Asians (loci in/near ADIPOQ, CDH13, WDR11FGF, CMIP, and PEPD) were assessed for their associations with the metabolic disorders. Being metabolically unhealthy was defined by exhibiting any metabolic syndrome component.

RESULTS

Among the six loci, ADIPOQ rs6773957 (OR 1.26, 95% CI:1.07-1.47, P = 0.004) and adiponectin receptor CDH13 rs4783244 (0.82, 0.69-0.96, P = 0.017) were correlated with metabolic risks independent of lifestyle factors in normal-weight children, but the associations were less obvious in those with overweight/obesity. A significant interaction between rs6773957 and diet (P_interaction = 0.004) for metabolic health was observed in normal-weight children. The adiponectin-decreasing allele of rs6773957 was associated with greater metabolic risks in individuals with unfavorable diet patterns (P < 0.001), but not in those with healthy patterns (P > 0.1). A similar interaction effect was observed using longitudinal data (P_interaction = 0.029).

CONCLUSIONS

These findings highlight a novel gene-diet interaction on the susceptibility to cardiometabolic disorders, which has a long-term impact from childhood onward, particularly in those with normal weight. Personalized dietary advice in these individuals may be recommended as an early possible therapeutic measure to improve metabolic health.

The prognostic role of RBP-4 and adiponectin in patients with peripheral arterial disease undergoing lower limb endovascular revascularization

BACKGROUND

RBP4 is an adipokine with an established role in atherosclerosis, while adiponectin has unique anti-inflammatory properties. We investigated the association of RBP4 and adiponectin with the presence of symptomatic peripheral artery disease (PAD) and their possible prognostic role in major adverse cardiovascular events (MACE).

METHODS

We enrolled 168 consecutive patients with symptomatic, established PAD, requiring revascularization by endovascular means of any or both of their lower limbs. 88 age- and sex-matched subjects with less than 2 classical cardiovascular risk factors served as controls. Clinical parameters, glycemic and lipid profile, RBP4 and adiponectin levels were assayed. The occurrence of MACE was recorded during the 6-month follow-up and patients were assigned to MACE and non-MACE subgroups.

RESULTS

The presence of symptomatic PAD was significantly correlated with age, diabetes, hsCRP, RBP4 and low adiponectin levels (p < 0.05). After adjustment for age, RBP4 (β = 0.498, p < 0.001), and adiponectin (β = -0.288, p < 0.001) levels remained as independent predictors of PAD presence in the whole study cohort. At baseline, MACE subgroup appeared with higher RBP-4 and hsCRP serum levels than non-MACE subgroup (p < 0.001), but no differences were detected for adiponectin (p = 0.758). Serum RBP4 levels remained independent predictor of MACE (β = 0.455, p < 0.001) after adjustment for traditional cardiovascular risk factors.

CONCLUSIONS

High RBP4 and low adiponectin serum levels are independently associated with PAD presence. In addition, RBP4 is an independent predictor of MACE incidence in symptomatic PAD patients.

The aetiology and molecular landscape of insulin resistance

Insulin resistance, defined as a defect in insulin-mediated control of glucose metabolism in tissues - prominently in muscle, fat and liver - is one of the earliest manifestations of a constellation of human diseases that includes type 2 diabetes and cardiovascular disease. These diseases are typically associated with intertwined metabolic abnormalities, including obesity, hyperinsulinaemia, hyperglycaemia and hyperlipidaemia. Insulin resistance is caused by a combination of genetic and environmental factors. Recent genetic and biochemical studies suggest a key role for adipose tissue in the development of insulin resistance, potentially by releasing lipids and other circulating factors that promote insulin resistance in other organs. These extracellular factors perturb the intracellular concentration of a range of intermediates, including ceramide and other lipids, leading to defects in responsiveness of cells to insulin. Such intermediates may cause insulin resistance by inhibiting one or more of the proximal components in the signalling cascade downstream of insulin (insulin receptor, insulin receptor substrate (IRS) proteins or AKT). However, there is now evidence to support the view that insulin resistance is a heterogeneous disorder that may variably arise in a range of metabolic tissues and that the mechanism for this effect likely involves a unified insulin resistance pathway that affects a distal step in the insulin action pathway that is more closely linked to the terminal biological response. Identifying these targets is of major importance, as it will reveal potential new targets for treatments of diseases associated with insulin resistance.

Adiponectin and cardiometabolic trait and mortality: where do we go?

Adiponectin is an adipocyte-derived cytokine known for its cardioprotective effects in preclinical studies. Early epidemiologic studies replicated these findings and drew great interest. Subsequent large-scale prospective cohorts, however, showed that adiponectin levels seemed not to relate to incident coronary artery disease (CAD). Even more surprisingly, a paradoxical increase of all-cause and cardiovascular (CV) mortality with increased adiponectin levels was reported. The adiponectin-mortality paradox has been explained by some groups asserting that adiponectin secretion is promoted by elevated natriuretic peptides (NP). Other groups have proposed that adiponectin is elevated due to adiponectin resistance in subjects with metabolic syndrome or heart failure (HF). However, there is no unifying theory that can clearly explain this paradox. In patients with HF with reduced ejection fraction (HFrEF), stretched cardiomyocytes secrete NPs, which further promote release of adiponectin from adipose tissue, leading to adiponectin resistance. On the other hand, adiponectin biology may differ in patients with heart failure with preserved ejection fraction (HFpEF), which constitutes 50% of all of HF. Most HFpEF patients are obese, which exerts inflammation and myocardial stiffness, that is likely to prevent myocardial stretch and subsequent NP release. This segment of the patient population may display a different adiponectin biology from its HFrEF counterpart. Dissecting the adiponectin-mortality relation in terms of different HF subtypes may help to comprehensively understand this paradox. Mendelian Randomization (MR) analyses claimed that adiponectin levels are not causally related to CAD or metabolic syndrome. Results from MR studies, however, should be interpreted with great caution because the underlying history of CAD or CHF were not taken into account in these analyses, an issue that may substantially confound the results. Here, we discuss many aspects of adiponectin; cardiometabolic traits, therapeutic interventions, and the ongoing debate about the adiponectin paradox, which were recently described in basic, epidemiologic, and clinical studies.

Causal Relationship between Adiponectin and Diabetic Retinopathy: A Mendelian Randomization Study in an Asian Population

Adiponectin (APN) is suggested to be a potential biomarker for predicting diabetic retinopathy (DR) risk, but the association between APN and DR has been inconsistent in observational studies. We used a Mendelian randomization (MR) analysis to evaluate if circulating APN levels result in DR. We applied three different genetic risk scores (GRS): GRS_All combined all 47 single nucleotide polymorphisms (SNPs), which from a genome-wide association study (GWAS) database-catalog reach significance level; GRS_Limited comprised 16 GRS_All-SNPs with a rigorous threshold (p < 5.0 × 10^-8 for GWAS), and GRS_APN combined 5 SNPs significantly associated with APN level. The MR-inverse-variance weighted method analysis showed that for each 1-SD increase in genetically induced increase in plasma APN, the OR of having DR was β = 0.20 (95% CI: -0.46-0.85, p = 0.553) for GRS_APN, 0.61 (95% CI: 0.10-1.13, p = 0.020) for GRS_All, and 0.57 (95% CI: -0.06 to 1.20, p = 0.078) for GRS_Limited. Sensitivity analysis, including MR-egger regression and the weighted-median approach, did not provide evidence of the pleiotropic effect of IVs. Limited evidence for the causal role of APN in DR risk among Taiwanese diabetic patients was shown based on MR analysis in the present study.

Adiponectin in Chronic Kidney Disease

Adiponectin is the adipokine associated with insulin sensitization, reducing liver gluconeogenesis, and increasing fatty acid oxidation and glucose uptake. Adiponectin is present in the kidneys, mainly in the arterial endothelium and smooth muscle cells, as well as in the capillary endothelium, and might be considered as a marker of many negative factors in chronic kidney disease. The last few years have brought a rising body of evidence that adiponectin is a multipotential protein with anti-inflammatory, metabolic, anti-atherogenic, and reactive oxygen species (ROS) protective actions. Similarly, adiponectin has shown many positive and direct actions in kidney diseases, and among many kidney cells. Data from large cross-sectional and cohort studies showed a positive correlation between serum adiponectin and mortality in chronic kidney disease. This suggests a complex interaction between local adiponectin action, comorbidities, and uremic milieu. In this review we discuss the role of adiponectin in chronic kidney disease.

Serum adipokines as non-invasive biomarkers in Crohn's disease

Adipose tissue secretes molecules that can promote activity in Crohn’s disease. We aimed to evaluate the role of serum adipokines as possible biomarkers in Crohn’s disease. Serum samples were obtained from 40 patients with endoscopically active or quiescent Crohn’s disease and 36 healthy controls. Serum leptin, ghrelin, resistin and adiponectin levels were analysed by Multiplex in a Luminex 200 system technology. Receiver Operating Characteristic curves were performed to evaluate the adipokines discriminatory capacity. A logistic regression adjusted by possible confounders (i.e. gender, age, BMI) was performed for those adipokines that showed an area under the curve > 0.7. No differences were found in age, gender or BMI among groups. Distribution for serum resistin was different among the three groups of study, and only this adipokine showed an area under the curve of 0.75 comparing actives patients and healthy control groups. Resistin median concentration was selected as a cut-off for a logistic regression analysis; odds ratio along its 95% confidence interval adjusted by gender, age, and BMI yielded a value of 5.46 (1.34–22.14) comparing actives patients and healthy controls. High concentration of serum resistin is probably associated to activity, being this association independent of gender, age or BMI.

Insights Into the Controversial Aspects of Adiponectin in Cardiometabolic Disorders

In 2016, the World Health Organization estimated that more than 1.9 billion adults were overweight or obese. This impressive number shows that weight excess is pandemic. Overweight and obesity are closely associated with a high risk of comorbidities, such as insulin resistance and its most important outcomes, including metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. Adiponectin has emerged as a salutary adipocytokine, with insulin-sensitizing, anti-inflammatory, and cardiovascular protective properties. However, under metabolically unfavorable conditions, visceral adipose tissue-derived inflammatory cytokines might reduce the transcription of the adiponectin gene and consequently its circulating levels. Low circulating levels of adiponectin are negatively associated with various conditions, such as insulin resistance, type 2 diabetes mellitus, metabolic syndrome, and cardiovascular disease. In contrast, several recent clinical trials and meta-analyses have reported high circulating adiponectin levels positively associated with cardiovascular mortality and all-cause mortality. These results are biologically intriguing and counterintuitive, and came to be termed "the adiponectin paradox". Adiponectin paradox is frequently associated with adiponectin resistance, a concept related with the downregulation of adiponectin receptors in insulin-resistant states. We review this contradiction between the apparent role of adiponectin as a health promoter and the recent evidence from Mendelian randomization studies indicating that circulating adiponectin levels are an unexpected predictor of increased morbidity and mortality rates in several clinical conditions. We also critically review the therapeutic perspective of synthetic peptide adiponectin receptors agonist that has been postulated as a promising alternative for the treatment of metabolic syndrome and type 2 diabetes mellitus.

Adiponectin in heart failure

The adipose tissue, apart from storing energy, plays a role of an endocrine organ. One of the most important adipokines secreted by adipose tissue is adiponectin, which is also produced by cardiomyocytes and connective tissue cells within the heart. Adiponectin is known for its beneficial effect on the metabolism and cardiovascular system and its low level is a factor of development of many cardiovascular diseases. Paradoxically, in the course of heart failure, adiponectin level gradually increases with the severity of the disease and higher adiponectin level is a factor of poor prognosis. As a result, there is a growing interest in adiponectin as a marker of heart failure progression and a predictor of prognosis in the course of this disease.

Elevated levels of adiponectin associated with major adverse cardiovascular and cerebrovascular events and mortality risk in ischemic stroke

BACKGROUND

Adiponectin plays role in multiple metabolic pathways. Previous studies in cardiovascular disease evaluated the association between adiponectin and clinical outcomes, yielding conflicting results. The aim of this study was to investigate the association of adiponectin with major adverse cardiovascular and cerebrovascular events (MACCE) and mortality in Chinese patients with first-ever acute ischemic stroke (AIS).

METHODS

This was a prospective, multicenter cohort study. From September 2009 through October 2015, all patients with AIS from 3 stroke centers in Shandong were included. Serum levels of adiponectin at admission were tested. The prognostic role of adiponectin to predict the MACCE and mortality within 3 years was evaluated by multivariable-adjusted Cox proportional hazards models.

RESULTS

This study included 4274 patients (median age 68 years [interquartile ranges {IQR}: 61-76]; 53.2% men). There were 794 deaths and 899 MACCE events. Higher serum levels of adiponectin on admission were found in patients with MACCE events and nonsurvivors (P < 0.001 and P < 0.001). In multivariable models adjusted for factors that confirmed in the univariate model, elevated serum levels of adiponectin were associated with a higher risk of MACCE (Quartile[Q]4 vs. Q1, Hazard ratio[HR] = 4.95 [95% confidence interval {CI}: 3.03-7.06]) and mortality (Q4 vs. Q1, HR = 5.63 [95% CI 3.15-7.99]). Adiponectin improved the prognostic value of the National Institutes of Health Stroke Scale (NIHSS) to predict MACCE (combined areas under the curve [AUC], 0.76; 95% CI 0.68-0.88; P = 0.001) and mortality (0.78[0.69-0.91]; P < 0.01). Subgroups analysis indicated that the prognostic role of adiponectin was more pronounced in women and patients with high levels of N-terminal-pro B-type natriuretic peptide(NT-pro BNP) (P < 0.001 and P < 0.001).

CONCLUSIONS

Elevated serum levels of adiponectin were associated with a higher risk of MACCE and mortality independent of traditional risk factors in ischemic stroke patients.

Obesity and cardiovascular disease in women

As the prevalence of obesity continues to grow worldwide, the health and financial burden of obesity-related comorbidities grows too. Cardiovascular disease (CVD) is clearly associated with increased adiposity. Importantly, women are at higher risk of CVD when obese and insulin resistant, in particular at higher risk of developing heart failure with preserved ejection fraction and ischemic heart disease. Increased aldosterone and mineralocorticoid receptor activation, aberrant estrogenic signaling and elevated levels of androgens are among some of the proposed mechanisms explaining the heightened CVD risk. In addition to traditional cardiovascular risk factors, understanding nontraditional risk factors specific to women, like excess weight gain during pregnancy, preeclampsia, gestational diabetes, and menopause are central to designing personalized interventions aimed to curb the epidemic of CVD. In the present review, we examine the available evidence supporting a differential cardiovascular impact of increased adiposity in women compared with men and the proposed pathophysiological mechanisms behind these differences. We also discuss women-specific cardiovascular risk factors associated with obesity and insulin resistance.

Higher Circulating Adiponectin Concentrations Predict Incident Cancer in Type 2 Diabetes - The Adiponectin Paradox

INTRODUCTION

Despite the beneficial cardiometabolic effects of adiponectin demonstrated in preclinical studies, paradoxically higher circulating adiponectin concentrations have been found in epidemiological studies to be associated with incident cardiovascular events, renal outcomes, and mortality in patients with diabetes. On the other hand, diabetes is also associated with an increased risk of cancer. Here, we investigated prospectively the association between circulating adiponectin concentrations and incident cancer using a cohort of exclusively individuals with type 2 diabetes.

MATERIALS AND METHODS

Baseline serum adiponectin concentrations were measured in 5658 participants recruited from the Hong Kong West Diabetes Registry. The associations of circulating adiponectin concentrations with incident cancer and cancer-related deaths were evaluated using multivariable Cox regression analysis, with hazard ratio (HR) for adiponectin referring to the respective risk per doubling of serum adiponectin concentration.

RESULTS

Over a median-follow up of 6.5 years, 7.53% and 3% of participants developed cancer and had cancer-related deaths, respectively. Serum adiponectin concentrations were significantly higher in those who had incident cancer (9.8 μg/mL vs 9.1 μg/mL, P < 0.001) and cancer-related deaths (11.5 μg/mL vs 9.3 μg/mL, P < 0.001) compared with those without. Moreover, in multivariable analyses, serum adiponectin concentration was independently associated with both incident cancer (hazard ratio, 1.19; 95% confidence interval, 1.05-1.35; P = 0.006) and cancer-related deaths (hazard ratio, 1.23; 95% confidence interval, 1.03-1.47; P = 0.024).

CONCLUSIONS

Higher serum adiponectin concentration was independently associated with incident cancer and cancer-related deaths in type 2 diabetes, indicating that adiponectin paradox can be observed in another major diabetic complication in addition to cardiovascular and kidney diseases.

Links Between Adiponectin and Dementia: From Risk Factors to Pathophysiology

With the aging population, dementia is becoming one of the most serious and troublesome global public health issues. Numerous studies have been seeking for effective strategies to delay or block its progression, but with little success. In recent years, adiponectin (APN) as one of the most abundant and multifunctional adipocytokines related to anti-inflammation, regulating glycogen metabolism and inhibiting insulin resistance (IR) and anti-atherosclerosis, has attracted widespread attention. In this article, we summarize recent studies that have contributed to a better understanding of the extent to which APN influences the risks of developing dementia as well as its pathophysiological progression. In addition, some controversial results interlinked with its effects on cognitive dysfunction diseases will be critically discussed. Ultimately, we aim to gain a novel insight into the pleiotropic effects of APN levels in circulation and suggest potential therapeutic target and future research strategies.

Effects of Adiponectin on T2DM and Glucose Homeostasis: A Mendelian Randomization Study

PURPOSE

The associations of adiponectin with type 2 diabetes mellitus (T2DM), glucose homeostasis (including β-cell function index (HOMA-β), insulin resistance (HOMA-IR), fasting insulin (FI) and fasting glucose (FG)) have reported in epidemiological studies. However, the previous observational studies are prone to biases, such as reverse causation and residual confounding factors. Herein, a Mendelian Randomization (MR) study was conducted to determine whether causal effects exist among them.

MATERIALS AND AND METHODS

Two-sample MR analyses and multiple sensitivity analyses were performed using the summary data from the ADIPOGen consortium, MAGIC Consortium, and a meta-analysis of GWAS with a considerable sample of T2DM (62,892 cases and 596,424 controls of European ancestry). We got eight valid genetic variants to predict the causal effect among adiponectin and T2DM and glucose homeostasis after excluding the probable invalid or pleiotropic variants.

RESULTS

Adiponectin was not associated with T2DM (odds ratio (OR) = 1.004; 95% confidence interval (CI): 0.740, 1.363) when using MR Egger after removing the invalid SNPs, and the results were consistent when using the other four methods. Similar results existed among adiponectin and HOMA-β, HOMA-IR, FI, FG.

CONCLUSION

Our MR study revealed that adiponectin had no causal effect on T2DM and glucose homeostasis and that the associations among them in observational studies may be due to confounding factors.

Discovery of potential plasma protein biomarkers for acute myocardial infarction via proteomics

Background

Acute myocardial infarction (AMI) is an acute disease with high mortality and seriously threatens human health. The identification of new effective biological markers for AMI is a prerequisite for treatment. Most proteomic studies have focused on atherosclerotic plaques, vascular cells, monocytes and platelets in the blood; however, the concentration of these factors in plasma is low, making it difficult to measure the complexity of plasma components. Moreover, some studies have examined the plasma protein of patients with acute coronary syndrome with histochemistry; however, the results are not consistent. Therefore, it is necessary to further investigate the differential proteins in the plasma of patients with AMI via proteomics to identify new biomarkers of AMI.

Methods

In this study, immunodepletion of high-abundance plasma proteins followed by an isobaric tagging for relative and absolute quantitation (iTRAQ)-based quantitative proteomic approach was used to analyze plasma samples from 5 control individuals and 10 AMI patients.

Results

Four hundred sixty-eight proteins were identified from two samples, and 33 proteins were differentially expressed in AMI patients compared to the controls. Among the 33 proteins, 12 proteins showed a ≥1.5-fold change between AMI and control samples. These proteins included fatty acid binding protein 3 (FABP3, ratio =6.36), creatine kinase-MB (CK-MB ratio =4.89), adenylate kinase1 (AK1 ratio =4.16), pro-platelet basic protein (PPBP ratio =3.29), creatine kinase (CK ratio =2.88), platelet factor 4 (PF4 ratio =2.62), peptidyl prolyl isomerase Cyclophilin A (PPIA ratio =2.05), Cofilin-1 (CFL1 ratio =1.81), coronin1A (CORO1A ratio =1.71), protein kinase M (PKM ratio =1.63), ribonuclease inhibitor (RNH1, ratio =1.67), and triose phosphate isomerase (TPI1 ratio =1.56). By contrast, there was a decrease of 19 proteins, such as adiponectin (ADIPOQ ratio =0.70), insulin-like growth factor binding protein6 (IGFBP6 ratio =0.70), Dickkopf-related protein 3 (DKK3 ratio =0.70) and complement 4B (C4B ratio =0.68). The most over-represented term was regulation of cell proliferation in the cellular component category of Gene Ontology (GO). The top 3 biological process terms were regulation of cell proliferation, response to wounding and wound healing. These proteins included immune proteins, blood coagulation proteins, lipid metabolism proteins, cytoskeleton proteins, energy metabolism proteins, gene regulation proteins, myocutaneous proteins, and myocardial remodeling proteins and were highly connected with each other, which indicates that the functional network of these processes contribute to the pathophysiology of AMI.

Conclusions

In conclusion, the present quantitative proteomic study identified novel AMI biomarker candidates and might provide fundamental information for the development of an AMI biomarker.

The association between serum adiponectin and 3-month outcome after ischemic stroke

BACKGROUND

Although adiponectin is a major adipocytokine that affects the pathogenesis of various cardiovascular diseases, its clinical significance in stroke remains controversial. The purpose of this study was to assess the impact of serum adiponectin levels on functional prognosis in patients with ischemic stroke.

METHODS

This was a prospective, observational cohort study. Consecutive first-ever ischemic stroke patients without any pre-morbid handicap admitted to our hospital were identified from December 2017 to December 2018. Serum concentration of adiponectin was routinely measured within the first 24 h after admission by a commercially available sandwich ELISA. Associations between adiponectin and either clinical severity at admission, poor outcomes or mortality at 3-month after admission were analyzed using logistic regression to obtain odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

The serum level of adiponectin was obtained in 227 patients with a median value of 7.0 μg/ml, which was significantly higher (P < 0.001) than in those heathy control. Adiponectin levels were associated with moderate-to-high stroke, and risk increased by 12% (OR = 1.12; 95% CI 1.03-1.25; P = 0.002). Patients with a poor outcome and nonsurvivors had significantly increased adiponectin levels on admission (P < 0.001, all). In multivariate logistic regression analysis, adiponectin was an independent predictor of functional outcome and mortality, and risk increased by 24% (OR = 1.24, 95% CI 1.13-1.37; P < 0.001) and 31% (1.31 [1.18-1.46], P < 0.001), respectively. Kaplan-Meier analysis suggested that the patients with high serum adiponectin levels had a higher risk of death than those patients with low levels (log-rank test P < 0.001).

CONCLUSIONS

Our results show that high adiponectin is associated with stroke severity and support the hypothesis that adiponectin can be serve as a biomarker of poor outcome after stroke, independent of baseline variables. Trial registration ChiCTR-OPC-17013501. Retrospectively Registered 21 September 2017.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Circulating adiponectin levels are paradoxically associated with mortality rate. A systematic review and meta-analysis

CONTEXT

Some studies have surprisingly indicated that serum adiponectin is positively related to mortality rate, thus casting doubts on its role as a therapeutic target for cardiovascular disease.

OBJECTIVE

To summarize evidence about direction, strength and modulators of this controversial association.

DATA SOURCES

MEDLINE, Web of Science, CINHAL, Cochrane Library and Scopus from inception through June 2018.

STUDY SELECTION

English-language prospective studies reporting the association between adiponectin and all-cause or cardiovascular mortality.

DATA EXTRACTION

Two investigators independently extracted data and assessed study quality using standard criteria following the Preferred Reporting Items for Systematic Reviews and Meta-analyses and The Newcastle-Ottawa Scale, respectively. Pooled hazard ratios (HRs) (95% confidence intervals-CIs) were derived using a fixed or random effects models when appropriated and were expressed for one standard deviation (SD) increment of adiponectin.

DATA SYNTHESIS

We identified fifty-five (n=61,676 subjects) and twenty-eight (n=43,979 subjects) studies for all-cause and cardiovascular mortality, respectively. Pooled HRs, were 1.24 (1.17-1.31) and 1.28 (1.19-1.37) for all-cause and cardiovascular mortality, respectively. Similar results were obtained also for High Molecular Weight adiponectin. When meta-analyses were restricted to studies reporting data on natriuretic peptides a 43% and 28% reduction on a log scale of these associations were observed after natriuretic peptides adjustment.

CONCLUSIONS

Our results strongly points to a paradoxical association between high adiponectin levels and increased mortality rate, which is partly modulated by natriuretic peptides.

Perivascular adipose tissue (PVAT) in atherosclerosis: a double-edged sword

Perivascular adipose tissue (PVAT), the adipose tissue that surrounds most of the vasculature, has emerged as an active component of the blood vessel wall regulating vascular homeostasis and affecting the pathogenesis of atherosclerosis. Although PVAT characteristics resemble both brown and white adipose tissues, recent evidence suggests that PVAT develops from its own distinct precursors implying a closer link between PVAT and vascular system. Under physiological conditions, PVAT has potent anti-atherogenic properties mediated by its ability to secrete various biologically active factors that induce non-shivering thermogenesis and metabolize fatty acids. In contrast, under pathological conditions (mainly obesity), PVAT becomes dysfunctional, loses its thermogenic capacity and secretes pro-inflammatory adipokines that induce endothelial dysfunction and infiltration of inflammatory cells, promoting atherosclerosis development. Since PVAT plays crucial roles in regulating key steps of atherosclerosis development, it may constitute a novel therapeutic target for the prevention and treatment of atherosclerosis. Here, we review the current literature regarding the roles of PVAT in the pathogenesis of atherosclerosis.

Low Molecular Weight Adiponectin Increases the Mortality Risk in Very Old Patients

Despite its beneficial role on insulin resistance and atherosclerosis, adiponectin has been frequently reported as an independent positive predictor of cardiovascular mortality. Very few information is available regarding adiponectin isoforms and mortality, in particular in advanced aging. Baseline serum levels of Total Adiponectin and its circulating isoforms (HMW-, MMW-, LMW-Adiponectin) were measured in 97 old patients (mean age: 79 years). Patients were followed up for all-cause mortality (study end-point) for an average of 76.4 ± 37.3 months. A positive association was observed for LMW-Ad and all-cause mortality (HR: 1.13, 95% CI: 1.05-1,22, p: 0.002). After multivariate adjustment for age, sex and a previous history of myocardial infarction, higher levels of LMW-Ad were significantly associated with all-cause mortality (HR: 1.11, 95% CI: 1.02-1.21; p: 0.017). Interestingly neither total adiponectin neither the other two circulating isoforms (MMW- and HMW-Ad) showed any significant association with the study end-point. Our data suggest that the association between high serum adiponectin levels and increased mortality rate in elderly is contingent to an unbalanced circulating levels of adiponectin isoforms. The present results support the hypothesis that high levels of Low Molecular Weight adiponectin are a biomarker for mortality risk in very old patients.

Metabolomic profiling implicates adiponectin as mediator of a favorable lipoprotein profile associated with NT-proBNP

Background

The N-terminal prohormone of brain natriuretic peptide (NT-proBNP) is an important biomarker for the diagnosis of heart failure. Apart from this and only recently recognized, NT-proBNP levels associate with higher HDL- and lower LDL-cholesterol levels comprising a favorable blood lipid profile. To further examine this observation, the lipoprotein profile in relation to NT-proBNP was examined in-depth by proton nuclear magnetic resonance spectroscopy (¹H-NMR). We complemented this investigation with a state-of-the-art untargeted metabolomics approach.

Methods

Lipoprotein particles were determined by ¹H-NMR spectroscopy in 872 subjects without self-reported diabetes from the population-based Study of Health in Pomerania (SHIP)-TREND with available NT-proBNP measurements. Comprehensive metabolomics data for plasma and urine samples were obtained. Linear regression models were performed to assess the associations between serum concentrations of NT-proBNP and the metabolites/lipoprotein particles measured in plasma or urine.

Results

An increase in serum NT-proBNP was associated with a benefical lipoprotein profile, including a decrease in VLDL, IDL and LDL-particles along with an increase in large HDL particles. These findings were replicated in a second independent cohort. Serum concentrations of NT-proBNP showed significant inverse associations with seven plasma metabolites while associations with 39 urinary metabolites, mostly comprising amino acids and related intermediates, were identified. Mediation analyses revealed adiponection as mediating factor for the associations observed with lipoproteins particles.

Conclusions

Most of the metabolic changes associated with NT-proBNP implicate significant influence on the blood lipid profile besides vasodilatory and the diuretic action of BNP signaling. Our data suggest that the more favorable lipoprotein profile as associated with elevated NT-proBNP concentrations in mainly cardiac healthy individuals might relate to adiponectin signaling indicating even indirect cardio-protective effects for NT-proBNP.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0765-1) contains supplementary material, which is available to authorized users.

Cardiovascular and inflammatory mechanisms in healthy humans exposed to air pollution in the vicinity of a steel mill

Background

There is a paucity of mechanistic information that is central to the understanding of the adverse health effects of source emission exposures. To identify source emission-related effects, blood and saliva samples from healthy volunteers who spent five days near a steel plant (Bayview site, with and without a mask that filtered many criteria pollutants) and at a well-removed College site were tested for oxidative stress, inflammation and endothelial dysfunction markers.

Methods

Biomarker analyses were done using multiplexed protein-array, HPLC-Fluorescence, EIA and ELISA methods. Mixed effects models were used to test for associations between exposure, biological markers and physiological outcomes. Heat map with hierarchical clustering and Ingenuity Pathway Analysis (IPA) were used for mechanistic analyses.

Results

Mean CO, SO₂ and ultrafine particles (UFP) levels on the day of biological sampling were higher at the Bayview site compared to College site. Bayview site exposures “without” mask were associated with increased (p < 0.05) pro-inflammatory cytokines (e.g IL-4, IL-6) and endothelins (ETs) compared to College site. Plasma IL-1β, IL-2 were increased (p < 0.05) after Bayview site “without” compared to “with” mask exposures. Interquartile range (IQR) increases in CO, UFP and SO₂ were associated with increased (p < 0.05) plasma pro-inflammatory cytokines (e.g. IL-6, IL-8) and ET-1_(1–21) levels. Plasma/saliva BET-1 levels were positively associated (p < 0.05) with increased systolic BP. C-reactive protein (CRP) was positively associated (p < 0.05) with increased heart rate. Protein network analyses exhibited activation of distinct inflammatory mechanisms after “with” and “without” mask exposures at the Bayview site relative to College site exposures.

Conclusions

These findings suggest that air pollutants in the proximity of steel mill site can influence inflammatory and vascular mechanisms. Use of mask and multiple biomarker data can be valuable in gaining insight into source emission-related health impacts.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0270-4) contains supplementary material, which is available to authorized users.

The relation between body fat distribution, plasma concentrations of adipokines and the metabolic syndrome in patients with clinically manifest vascular disease

Introduction

We evaluated the relationship between adipokine plasma concentrations and body fat distribution and the metabolic syndrome.

Methods

In a cohort of 1215 patients with clinically manifest vascular disease the relation between subcutaneous adipose tissue, visceral adipose tissue, waist circumference, body mass index and plasma concentrations of adipsin, chemerin, monocyte chemoattractant protein-1, migration inhibitory factor, nerve growth factor, resistin, plasma amyloid A1, adiponectin, leptin, plasminogen activator inhibitor-1 and hepatic growth factor were cross-sectionally assessed with linear regression and adjusted for age and gender. The relation between adipokines and the metabolic syndrome was cross-sectionally evaluated using logistic regression. An adipokine profile was developed to measure the effect of combined rather than single adipokines.

Results

Adiposity was related to higher nerve growth factor, hepatic growth factor, migration inhibitory factor, leptin and adipsin and with lower chemerin, plasminogen activator inhibitor-1, resistin, plasma amyloid A1 and adiponectin. The strongest positive relations were between body mass index and adipsin (β 0.247; 95% CI 0.137–0.356) and leptin (β 0.266; 95% CI 0.207–0.324); the strongest negative relations were between body mass index and plasma amyloid A1 (β –0.266; 95% CI –0.386 to –0.146) and visceral adipose tissue and adiponectin (β –0.168; 95% CI –0.226 to –0.111). There was no relation between subcutaneous adipose tissue and adipokines. Odds for the metabolic syndrome were higher with each 1 SD higher hepatic growth factor (OR 1.21; 95% CI 1.06–1.38) and leptin (OR 1.26; 95% CI 1.10–1.45) and lower with each 1 SD higher adiponectin (OR 0.73; 95% CI 0.64–0.83) and resistin (OR 0.85; 95% CI 0.74–0.97). The adipokine profile was related to the metabolic syndrome (OR 1.03; 95% CI 1.00–1.06).

Conclusion

Plasma concentrations of adipokines are related to obesity and body fat distribution. The relation between adipokine concentrations and the metabolic syndrome is independent of visceral adipose tissue.

Resistin Is a Novel Marker for Postoperative Pain Intensity

BACKGROUND

Pro- and anti-inflammatory cytokines (adipokines) associated with adipose tissue can modulate inflammatory processes and lead to systemic inflammatory conditions such as metabolic syndrome. In the present pilot study, we investigated 3 major adipokines (leptin, adiponectin, and resistin) and 2 nonspecific proinflammatory cytokines (tumor necrosis factor α and interleukin-6) with regard to their association with postoperative pain intensity.

METHODS

We analyzed a total of 45 single-nucleotide polymorphisms of the adipokines in 57 patients with postlaparotomy pain. We adjusted for multiple testing to reduce the chance of false-positive results by controlling the false discovery rate. Serum levels of the adipokines and proinflammatory cytokines were measured in another 36 patients undergoing laparotomy. A stepwise multiple linear regression analysis using these measurements and opioid dosages as independent variables was performed to explore the factors associated with postoperative pain.

RESULTS

Only 1 variant of the resistin gene (rs3745367) demonstrated a significant association with postoperative pain (P < .002). Patients exhibiting homozygosity for the minor alleles (n = 7; numerical rating scale [NRS], 2.3 ± 1.3) demonstrated lower pain intensity compared with those exhibiting homozygosity for the major alleles (n = 29; NRS, 3.8 ± 1.0; P = .004) and heterozygosity for the minor alleles (n = 21; NRS, 4.2 ± 0.8; P < .001). Only serum resistin levels showed a positive association with postoperative pain.

CONCLUSIONS

A genetic variant of resistin and serum resistin levels were associated with postoperative pain intensity, while other adipokines and cytokines exhibit no such association. Resistin can alter the inflammatory responses in postoperative wounds, although it could be a determinant factor that is independent of inflammatory processes. Resistin may be a novel marker for postoperative pain intensity.

The Adiponectin Paradox for All-Cause and Cardiovascular Mortality

Basic science studies have shown beneficial effects of adiponectin on glucose homeostasis, chronic low-grade inflammation, apoptosis, oxidative stress, and atherosclerotic processes, so this molecule usually has been considered a salutary adipokine. It was therefore quite unexpected that large prospective human studies suggested that adiponectin is simply a marker of glucose homeostasis, with no direct favorable effect on the risk of type 2 diabetes and cardiovascular disease. But even more unforeseen were data addressing the role of adiponectin on the risk of death. In fact, a positive, rather than the expected negative, relationship was reported between adiponectin and mortality rate across many clinical conditions, comprising diabetes. The biology underlying this paradox is unknown. Several explanations have been proposed, including adiponectin resistance and the confounding role of natriuretic peptides. In addition, preliminary genetic evidence speaks in favor of a direct role of adiponectin in increasing the risk of death. However, none of these hypotheses are based on robust data, so further efforts are needed to unravel the elusive role of adiponectin on cardiometabolic health and, most important, its paradoxical association with mortality rate.

Human epicardial adipose tissue-derived and circulating secreted frizzled-related protein 4 (SFRP4) levels are increased in patients with coronary artery disease

Background

Previous studies have demonstrated that secreted frizzled-related protein 4 (SFRP4) is associated with impaired glucose and triglyceride metabolism in patients with stable coronary artery disease. In the present study, we investigated human epicardial adipose tissue (EAT)-derived and circulating SFRP4 levels in patients with coronary artery disease (CAD).

Methods

Plasma samples and adipose biopsies from EAT and subcutaneous adipose tissue (SAT) were collected from patients with CAD (n = 40) and without CAD (non-CAD, n = 30) during elective cardiac surgery. The presence of CAD was identified by coronary angiography. SFRP4 mRNA and protein expression levels in adipose tissue were detected by quantitative real-time PCR and immunohistochemistry, respectively. Plasma SFRP4 concentrations were measured by an enzyme-linked immunosorbent assay (ELISA). Correlation analysis and multivariate linear regression analysis were used to determine the association of SFRP4 expression with atherosclerosis as well as clinical risk factors.

Results

SFRP4 mRNA and protein expression levels were significantly lower in EAT than in paired SAT in patients with and without CAD (all P < 0.05). Compared to non-CAD patients, CAD patients had higher SFRP4 expression levels in EAT (both mRNA and protein levels) and in plasma. Multivariate linear regression analysis showed that CAD was an independent predictor of SFRP4 expression levels in EAT (beta = 0.442, 95% CI 0.030–0.814; P = 0.036) and in plasma (beta = 0.300, 95% CI 0.056–0.545; P = 0.017). SAT-derived SFRP4 mRNA levels were independently associated with fasting insulin levels (beta = 0.382, 95% CI 0.008–0.756; P = 0.045). In addition, plasma SFRP4 levels were positively correlated with BMI (r = 0.259, P = 0.030), fasting insulin levels (r = 0.306, P = 0.010) and homeostasis model assessment of insulin resistance (HOMA-IR) values (r = 0.331, P = 0.005).

Conclusions

EAT-derived and circulating SFRP4 expression levels were increased in patients with CAD. EAT SFRP4 mRNA levels and plasma SFRP4 concentrations were independently associated with the presence of CAD.

Circulating sortilin level as a potential biomarker for coronary atherosclerosis and diabetes mellitus

Context

A previous genome-wide association study showed that a genetic variant of sortilin was associated with the risk of coronary artery disease (CAD). However, the role of circulating sortilin is still unknown. We investigated the potential role of plasma sortilin as a biomarker for CAD and diabetes mellitus.

Methods

We enrolled statin-naïve subjects with CAD (n = 31) who underwent coronary artery bypass surgery and control subjects (n = 116) who were free from CAD as evaluated by coronary CT angiography. The presence of diabetes mellitus was evaluated and plasma sortilin levels were measured with a commercial ELISA kit.

Results

Plasma sortilin levels were higher in subjects with CAD and subjects with diabetes mellitus than in those without CAD or diabetes mellitus. Subjects in the highest sortilin tertile group were older and had higher glucose and HbA1c levels, but lipid profiles in the three tertile groups were comparable. Multivariable logistic regression analysis revealed that sortilin levels were independently associated with CAD. In addition, the receiver operating characteristic curve analysis showed that plasma sortilin levels could identify the presence of CAD or diabetes mellitus.

Conclusions

Elevated circulating sortilin levels are associated with CAD and diabetes mellitus and can be used as a biomarker of both diseases in statin-naïve subjects.

Westernization of lifestyle affects quantitative and qualitative changes in adiponectin

Background

Although Japanese–Americans and native Japanese share the same genetic predispositions, they live different lifestyles, resulting in insulin resistance in Japanese–Americans. We investigated whether the quantitative and qualitative changes in adiponectin (APN) due to differences in lifestyle contribute to the development of insulin resistance.

Methods

We evaluated 325 native Japanese in Hiroshima, Japan and 304 Japanese–Americans in Los Angeles, the United States, who were aged between 30 and 70 years and underwent medical examinations between 2009 and 2010. All participants underwent a 75-g oral glucose tolerance test (OGTT) to assess their glucose tolerance. The insulin response to oral glucose load, the Matsuda index, total APN levels, and C1q-APN/total-APN ratios were compared between native Japanese and Japanese–Americans.

Results

Compared with the native Japanese, the Japanese–Americans had significantly lower Matsuda index and higher area under the curve values for serum insulin concentration during OGTT in the normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) groups, but not in the diabetes mellitus (DM) group. Furthermore, the Japanese–Americans had significantly lower total APN levels and higher C1q-APN/total-APN ratios than the native Japanese in the NGT and IGT groups, but not in the DM group.

Conclusions

This study suggested that, in Japanese people, the westernization of their lifestyle might affect quantitative and qualitative changes in APN and induce insulin resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0565-z) contains supplementary material, which is available to authorized users.

Cardiovascular Adiponectin Resistance: The Critical Role of Adiponectin Receptor Modification

For the past two decades, a great deal of research has been published concerning adiponectin (APN), an abundant protein responsible for regulating numerous biologic functions including antioxidative, antinitrative, anti-inflammatory, and cardioprotective effects. A review of APN and its two major receptors is timely because of new findings concerning the mechanisms by which APN signaling may be altered in pathologic processes such as diabetes and heart failure. In this review we elaborate on currently known information regarding the physiologic role of APN and the known mechanisms underlying pathologic APN resistance - namely, APN receptor downregulation and phosphorylation - and provide insight regarding the future directions of APN research including an assessment of the clinical applicability of preventing pathologic post-translational modification of the APN receptor.

The Protective Effect of Apigenin on Myocardial Injury in Diabetic Rats mediating Activation of the PPAR-γ Pathway

We substantiated the role of peroxisome proliferator-activated receptor-γ (PPAR-γ) activation in the protective effect of apigenin against the myocardial infarction (MI) in diabetic rats. Diabetes was induced by intraperitoneal administration of a single dose of streptozotocin (55 mg/kg). The study groups included diabetic rats receiving vehicle, apigenin (75 mg/kg/day, orally), GW9662 (1 mg/kg/day, intraperitoneally), and a combination of apigenin and GW9662 for 14 days. The MI was induced in all the study groups except the diabetic control group by subcutaneous injection of 100 mg/kg/day of isoproterenol on the two terminal days. The diabetes and isoproterenol-induced MI was evident as a reduction in the maximal positive and negative rate of developed left ventricular pressure and an increase in the left ventricular end-diastolic pressure. The activities of creatine kinase on myocardial bundle (CK-MB) and lactate dehydrogenase (LDH) were also reduced. Apigenin treatment prevented the hemodynamic perturbations, restored the left ventricular function and reinstated a balanced redox status. It protected rats against an MI by attenuating myonecrosis, edema, cell death, and oxidative stress. GW9662, a PPAR-γ antagonist reversed the myocardial protection conferred by apigenin. Further, an increase in the PPAR-γ expression in the myocardium of the rats receiving apigenin reinforces the role of PPAR-γ pathway activation in the cardioprotective effects of apigenin.

Serum resistin is causally related to mortality risk in patients with type 2 diabetes: preliminary evidences from genetic data

Resistin has been firmly associated with all-cause mortality. We investigated, whether, in patients with type 2 diabetes (T2D), this association is sustained by a cause-effect relationship. A genotype risk score (GRS), created by summing the number of resistin increasing alleles of two genome-wide association studies (GWAS)-derived single nucleotide polymorphisms (SNPs), serum resistin measurements and all-cause death records were obtained in 1,479 (403 events/12,454 person-years), patients with T2D from three cohorts, Gargano Heart Study-prospective design (n = 350), Gargano Mortality Study (n = 698) and Foggia Mortality Study (n = 431), from Italy. GRS was strongly associated with serum resistin in a non-linear fashion (overall p = 3.5 * 10^-7) with effect size modest for GRS = 1 and 2 and much higher for GRS >3, with respect to GRS = 0. A significant non-linear association was observed also between GRS and all-cause mortality (overall p = 3.3 * 10^-2), with a low effect size for GRS = 1 and 2, and nearly doubled for GRS ≥ 3, with respect to GRS = 0. Based on the above-reported associations, each genetic equivalent SD increase in log-resistin levels showed a causal hazard ratio of all-cause mortality equal to 2.17 (95%CI: 1.22-3.87), thus providing evidence for a causal role of resistin in shaping the risk of mortality in diabetic patients.

Circulating cytokines as determinants of weight loss-induced improvements in insulin sensitivity

Dietary calorie restriction and exercise promote weight loss and may have additive effects for improving insulin sensitivity, independent of weight loss. It is not known if these effects are attributable to changes in circulating cytokines. We evaluated the hypothesis that modest, matched weight loss induced by calorie restriction and exercise have additive effects on circulating cytokines and these changes correlate with improvements in insulin sensitivity. Overweight and sedentary women and men (n = 52, 45-65 years) were randomized to undergo 7 % weight loss by using 3-6 months of calorie restriction, exercise, or a combination of both calorie restriction and exercise. Concentrations of cytokines and hormones were measured in fasting and oral glucose tolerance test blood samples. Insulin sensitivity was estimated based on oral glucose tolerance test for glucose and insulin. With all groups combined, fasting leptin (p < 0.0001) and high molecular weight adiponectin (p = 0.04) decreased and pentraxin-3 increased (p < 0.0001), in a manner that correlated with improvements in insulin sensitivity (all p ≤ 0.0002). These changes, combined with decreases in glucose-dependent insulinotropic polypeptide from the oral glucose tolerance test, explained 63 % of the variance (p < 0.0001) in insulin sensitivity improvements. Exercise and calorie restriction had additive effects on leptin, with a similar trend for high molecular weight adiponectin. Monocyte chemoattractant protein-1 and C-reactive protein concentrations did not change. Calorie restriction and exercise had opposite effects on soluble tumor necrosis factor receptor-1. Modest weight loss in overweight adults decreases serum leptin and high molecular weight adiponectin, and increases pentraxin-3 concentrations in a manner that correlates with increased insulin sensitivity. Exercise has additive effects to those induced by calorie restriction for reductions in leptin and possibly adiponectin. These changes may contribute to the additive effects of calorie restriction and exercise for improving insulin sensitivity.

Interaction between β-hexachlorocyclohexane and ADIPOQ genotypes contributes to the risk of type 2 diabetes mellitus in East Chinese adults

Growing evidence links environmental exposure to hexachlorocyclohexanes (HCHs) to the risk of type 2 diabetes mellitus (T2DM), and ADIPOQ that encodes adiponectin is considered as an important gene for T2DM. However, the role of ADIPOQ-HCH interaction on T2DM risk remains unclear. Thus, a paired case-control study was conducted in an East Chinese community. A total of 1446 subjects, including 723 cases and 723 controls matched on age, gender and residence, were enrolled, and 4 types of HCH isomers were measured in serum samples using GC-MS/MS. Additionally, 4 candidate ADIPOQ SNPs (rs182052, rs266729, rs6810075, and rs16861194) were genotyped by TaqMan assay, and plasma adiponectin was measured using ELISA. No associations between 4 SNPs and T2DM risk were found, but T2DM risk significantly increased with serum levels of β-HCH (P < 0.001). Furthermore, the synergistic interaction between β-HCH and rs182052 significantly increased T2DM risk (OR _{I-additive model} = 2.20, OR _{I-recessive model} = 2.13). Additionally, individuals carrying only rs182052 (A allele) with high levels of β-HCH had significant reduction in adiponectin levels (P = 0.016). These results indicate that the interaction between rs182052 and β-HCH might increase the risk of T2DM by jointly decreasing the adiponectin level and potentially trigger T2DM development.

Metabolic Vascular Syndrome: New Insights into a Multidimensional Network of Risk Factors and Diseases

BACKGROUND

Since 1981, we have used the term metabolic syndrome to describe an association of a dysregulation in lipid metabolism (high triglycerides, low high-density lipoprotein cholesterol, disturbed glucose homeostasis (enhanced fasting and/or prandial glucose), gout, and hypertension), with android obesity being based on a common soil (overnutrition, reduced physical activity, sociocultural factors, and genetic predisposition). We hypothesized that main traits of the syndrome occur early and are tightly connected with hyperinsulinemia/insulin resistance, procoagulation, and cardiovascular diseases.

METHODS

To establish a close link between the traits of the metabolic vascular syndrome, we focused our literature search on recent original work and comprehensive reviews dealing with the topics metabolic syndrome, visceral obesity, fatty liver, fat tissue inflammation, insulin resistance, atherogenic dyslipidemia, arterial hypertension, and type 2 diabetes mellitus.

RESULTS

Recent research supports the concept that the metabolic vascular syndrome is a multidimensional and interactive network of risk factors and diseases based on individual genetic susceptibility and epigenetic changes where metabolic dysregulation/metabolic inflexibility in different organs and vascular dysfunction are early interconnected.

CONCLUSION

The metabolic vascular syndrome is not only a risk factor constellation but rather a life-long abnormality of a closely connected interactive cluster of developing diseases which escalate each other and should continuously attract the attention of every clinician.

Palaeolithic diet decreases fasting plasma leptin concentrations more than a diabetes diet in patients with type 2 diabetes: a randomised cross-over trial

Background

We have previously shown that a Palaeolithic diet consisting of the typical food groups that our ancestors ate during the Palaeolithic era, improves cardiovascular disease risk factors and glucose control compared to the currently recommended diabetes diet in patients with type 2 diabetes. To elucidate the mechanisms behind these effects, we evaluated fasting plasma concentrations of glucagon, insulin, incretins, ghrelin, C-peptide and adipokines from the same study.

Methods

In a randomised, open-label, cross-over study, 13 patients with type 2 diabetes were randomly assigned to eat a Palaeolithic diet based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts, or a diabetes diet designed in accordance with current diabetes dietary guidelines during two consecutive 3-month periods. The patients were recruited from primary health-care units and included three women and 10 men [age (mean ± SD) 64 ± 6 years; BMI 30 ± 7 kg/m²; diabetes duration 8 ± 5 years; glycated haemoglobin 6.6 ± 0.6 % (57.3 ± 6 mmol/mol)] with unaltered diabetes treatment and stable body weight for 3 months prior to the start of the study. Outcome variables included fasting plasma concentrations of leptin, adiponectin, adipsin, visfatin, resistin, glucagon, insulin, C-peptide, glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1 and ghrelin. Dietary intake was evaluated by use of 4-day weighed food records.

Results

Seven participants started with the Palaeolithic diet and six with the diabetes diet. The Palaeolithic diet resulted in a large effect size (Cohen’s d = −1.26) at lowering fasting plasma leptin levels compared to the diabetes diet [mean difference (95 % CI), −2.3 (−5.1 to 0.4) ng/ml, p = 0.023]. No statistically significant differences between the diets for the other variables, analysed in this study, were observed.

Conclusions

Over a 3-month study period, a Palaeolithic diet resulted in reduced fasting plasma leptin levels, but did not change fasting levels of insulin, C-peptide, glucagon, incretins, ghrelin and adipokines compared to the currently recommended diabetes diet.

Trial registration: ClinicalTrials.gov NCT00435240

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0398-1) contains supplementary material, which is available to authorized users.

Insulin resistance, endothelial function, angiogenic factors and clinical outcome in non-diabetic patients with chest pain without myocardial perfusion defects

Background

Patients with angina-like symptoms without myocardial perfusion scintigram (MPS)-verified abnormality may still be at risk for cardiovascular events. We hypothesized that insulin resistance could play a role in this population even without diagnosed diabetes. We further explored physiological and blood biomarkers, as well as global gene expression patterns that could be closely related to impaired glucose homeostasis to deepen our mechanistic understanding.

Methods

A total of 365 non-diabetic patients with suspected myocardial ischemia referred to MPS were enrolled and followed up regarding event-free survival with a median time of 5.1 years. All patients underwent endothelial function assessment by reactive hyperemic index (RHI) using EndoPAT and extensive biomarker analysis. Whole blood global gene expression pathway analysis was performed in a subset of patients.

Results

Homeostasis model assessment of insulin resistance (HOMA-IR) added independent prognostic value in patients without myocardial perfusion defects. In a multivariable analysis, HOMA-IR was inversely associated with low RHI. Furthermore, elevated HOMA-IR was associated with decreased levels of vascular endothelial growth factor D, stem cell factor and endocan as well as to increased level of interleukin-6. Global gene expression pathway analysis of whole blood cells showed that high HOMA-IR and impaired endothelial function were associated with upregulated pro-inflammatory pathways and down-regulated eukaryotic initiation factor-2 pathway.

Conclusions

Insulin resistance measured by HOMA-IR is associated with endothelial dysfunction and confers independent prognostic information in non-diabetic patients with chest pain without myocardial perfusion defects. Increased systemic pro-inflammatory state and decreased levels of pro-angiogenic vascular growth factors may be important underlying molecular mechanisms.