Insulin resistance and atherosclerosis: convergence between metabolic pathways and inflammatory nodes

Developmental endothelial locus-1 in cardiovascular and metabolic diseases: A promising biomarker and therapeutic target

Cardiovascular and metabolic diseases (CVMDs) are a leading cause of death worldwide and impose a major socioeconomic burden on individuals and healthcare systems, underscoring the urgent need to develop new drug therapies. Developmental endothelial locus-1 (DEL-1) is a secreted multifunctional domain protein that can bind to integrins and play an important role in the occurrence and development of various diseases. Recently, DEL-1 has attracted increased interest for its pharmacological role in the treatment and/or management of CVMDs. In this review, we present the current knowledge on the predictive and therapeutic role of DEL-1 in a variety of CVMDs, such as atherosclerosis, hypertension, cardiac remodeling, ischemic heart disease, obesity, and insulin resistance. Collectively, DEL-1 is a promising biomarker and therapeutic target for CVMDs.

Can the Serum Endocan Level Be Used as a Biomarker to Predict Subclinical Atherosclerosis in Patients with Prediabetes?

BACKGROUND

Patients with prediabetes have an increased risk of atherosclerotic cardiovascular disease; therefore, early detection is important.

OBJECTIVE

The present study aimed to reveal the usability of serum endocan levels as a biomarker in the diagnosis of subclinical atherosclerosis in patients with prediabetes, based on CIMT measurements.

METHODS

Participants were classified according to the presence (n=42) or absence (n=42) of prediabetes. Serum endocan, fasting blood sugar, fasting insulin, and glycated hemoglobin (HbA1c) values of patients were examined, and CIMT was measured. The level of significance for statistical analysis was 0.05.

RESULTS

While serum endocan levels were found to be lower in patients with prediabetes, when compared to the control group (p=0.042), CIMT values were found to be higher (p=0.046). When evaluated by multivariate regression analysis, the serum endocan level was found to be associated with CIMT, regardless of other parameters (p=0.007). A negative correlation was found between plasma fasting insulin and endocan levels (r=-0.320, p=0.001).

CONCLUSIONS

Carotid intima media thickness was found to be high and the serum endocan level was low in patients with prediabetes. Decreased serum endocan levels in patients with prediabetes may be a contributing factor to atherosclerosis formation mechanisms.

Vitamin D3 attenuates oxidative stress and regulates glucose level and leukocyte count in a semi-chronic streptozotocin-induced diabetes model

Purpose

Vitamin D3 (vit-D3) is a potent immunomodulator with anti-inflammatory and antioxidative properties. We used streptozotocin (STZ)-induced rat model of diabetes (DM) to evaluate the effects of vit-D3. We measured serum biochemical parameters, interleukin-17 (IL-17), osteocalcin (OC), malondialdehyde (MDA), and immune cell count on the 21st day of experiment.

Method

A total of 24 Wistar rats were randomly divided into three groups. Each group had eight rats. During the 1st day of the experiment, the control group was injected intraperitoneally with citrate buffer, while STZ group and STZ + vit-D3 group were injected by a single i.p. dose (35 mg/kg) of STZ dissolved in citrate buffer (pH 4,5; 0,1 M). Vitamin D3 was applied via oral gavage once daily to the STZ + vit-D3 group for a total period of 14 days, starting from the 7th day of the experiment.

Results

STZ rats showed a significant reduction in OC and an increase in MDA and IL-17 serum concentrations compared to the control rats. We also observed a significant STZ-associated decrease in the number of lymphocytes and a significant increase in monocyte and eosinophil number. Oral treatment with vit-D3 to STZ-induced diabetic rats significantly increased OC and decreased MDA serum levels. Furthermore, vit-D3 treatment resulted in a good regulation of hematopoiesis such as increase in the number of segmented granulocytes and lymphocytes and a reduction in the number of monocytes and eosinophils.

Conclusion

Vit-D3 treatment has important therapeutic effects; among many others it can attenuate oxidative stress and ameliorate the hyperglycemic state in the STZ-induced rat diabetic model, which is promising for further clinical trials.

Heart fat and carotid artery atherosclerosis progression in recently menopausal women: impact of menopausal hormone therapy: The KEEPS trial

OBJECTIVE

Heart fat deposition has been linked to atherosclerosis, and both accelerate after menopause. Hormone therapy (HT) may differentially slow heart fat deposition and progression of atherosclerosis, depending on the specific HT agent or its route of administration. Our objective was to evaluate the effects of different HT agents, oral and transdermal, on associations between heart fat accumulation and atherosclerosis progression, measured by carotid intima-media thickness (CIMT), in recently menopausal women from the Kronos Early Estrogen Prevention Study (KEEPS) trial.

METHODS

KEEPS was a randomized, placebo-controlled trial of the effects of 0.45 mg/d oral conjugated equine estrogens (o-CEE) or 50 mcg/d transdermal 17β-estradiol (t-E2), compared with placebo, on 48 months progression of CIMT. Epicardial adipose tissue (EAT) and paracardial adipose tissue (PAT) volumes were quantified by computed tomography.

RESULTS

In all, 467 women (mean age [SD] 52.7 [2.5]; 78.2% White; 30% on o-CEE, 30.8% t-E2, 39.2% placebo) with heart fat volumes and CIMT at baseline and 48 months were included. EAT and PAT changes were not associated with CIMT progression; however, the assigned treatment significantly modified the association between PAT (but not EAT) change and CIMT progression. In the o-CEE group, adjusted CIMT progression was 12.66 μm (95% confidence interval [CI] 1.80, 23.52) lower than in t-E2 group (P = 0.02), and 10.09 μm (95% CI 0.79, 19.39) lower than in placebo group (P = 0.03), as per 1-SD increase in PAT.

CONCLUSION

Compared with t-E2, o-CEE appears to slow down the adverse effect of increasing PAT on progression of atherosclerosis. Whether this beneficial association is specific to CEE or to the oral route of CEE administration is unclear and should be assessed further.

Association between asymptomatic intracranial arterial stenosis and insulin resistance or diabetes mellitus: a cross-sectional study in rural Shandong, China

INTRODUCTION

Recent studies have shown that insulin resistance (IR) is correlated to atherosclerosis development. However, few studies have investigated the association between IR and asymptomatic intracranial arterial stenosis (aICAS).

RESEARCH DESIGN AND METHODS

This cross-sectional study enrolled 2007 rural residents in China who were aged ≥40 years without a clinical history of stroke and transient ischaemic attack. We used transcranial Doppler ultrasonography in combination with magnetic resonance angiography to diagnose aICAS (stenosis ≥50%). IR was defined as a homeostasis model assessment of insulin resistance ≥3.0 based on the 75th percentile for all the participants. Multivariate logistic regression models were employed to assess the relationship of diabetic parameters with aICAS in all participants, as well as with aICAS in non-diabetic participants, and further stratified by sex.

RESULTS

After adjusting for age, gender, smoking habit, drinking habit, low-density lipoprotein cholesterol, raised blood pressure, triglycerides, high-density lipoprotein cholesterol and waist circumference, diabetes mellitus (DM) (OR=2.09, 95% CI 1.31 to 3.32), fasting plasma glucose (FPG) (OR=1.34, 95% CI 1.14 to 1.57), and IR (OR=1.75, 95% CI 1.11 to 2.75) were associated with aICAS in the total study population; however, these relationships remained significant only in men after the analyses were stratified by sex (DM: OR=3.40, 95% CI 1.62 to 7.13; FPG: OR=1.64, 95% CI 1.26 to 2.13; IR: OR=3.04, 95% CI 1.44 to 6.42). When further excluding the diabetic participants from the total study population, positive associations between IR and aICAS were similarly observed only in men (OR=4.65, 95% CI 1.69 to 12.82).

CONCLUSIONS

IR might predict the prevalence of aICAS independently of major cardiovascular risk factors and metabolic syndrome components among men living in rural China.

Loss of Hepatic Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 Links Nonalcoholic Steatohepatitis to Atherosclerosis

Patients with nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) commonly develop atherosclerosis through a mechanism that is not well delineated. These diseases are associated with steatosis, inflammation, oxidative stress, and fibrosis. The role of insulin resistance in their pathogenesis remains controversial. Albumin (Alb)Cre⁺Cc1^flox(fl)/fl mice with the liver‐specific null deletion of the carcinoembryonic antigen‐related cell adhesion molecule 1 (Ceacam1; alias Cc1) gene display hyperinsulinemia resulting from impaired insulin clearance followed by hepatic insulin resistance, elevated de novo lipogenesis, and ultimately visceral obesity and systemic insulin resistance. We therefore tested whether this mutation causes NAFLD/NASH and atherosclerosis. To this end, mice were propagated on a low‐density lipoprotein receptor (Ldlr)^−/− background and at 4 months of age were fed a high‐cholesterol diet for 2 months. We then assessed the biochemical and histopathologic changes in liver and aortae. Ldlr^−/−AlbCre⁺Cc1^fl/fl mice developed chronic hyperinsulinemia with proatherogenic hypercholesterolemia, a robust proinflammatory state associated with visceral obesity, elevated oxidative stress (reduced NO production), and an increase in plasma and tissue endothelin‐1 levels. In parallel, they developed NASH (steatohepatitis, apoptosis, and fibrosis) and atherosclerotic plaque lesions. Mechanistically, hyperinsulinemia caused down‐regulation of the insulin receptor followed by inactivation of the insulin receptor substrate 1–protein kinase B–endothelial NO synthase pathway in aortae, lowering the NO level. This also limited CEACAM1 phosphorylation and its sequestration of Shc‐transforming protein (Shc), activating the Shc–mitogen‐activated protein kinase–nuclear factor kappa B pathway and stimulating endothelin‐1 production. Thus, in the presence of proatherogenic dyslipidemia, hyperinsulinemia and hepatic insulin resistance driven by liver‐specific deletion of Ceacam1 caused metabolic and vascular alterations reminiscent of NASH and atherosclerosis. Conclusion: Altered CEACAM1‐dependent hepatic insulin clearance pathways constitute a molecular link between NASH and atherosclerosis.

Agent-based modeling and bifurcation analysis reveal mechanisms of macrophage polarization and phenotype pattern distribution

Macrophages play a key role in tissue regeneration by polarizing to different destinies and generating various phenotypes. Recognizing the underlying mechanisms is critical in designing therapeutic procedures targeting macrophage fate determination. Here, to investigate the macrophage polarization, a nonlinear mathematical model is proposed in which the effect of IL4, IFNγ and LPS, as external stimuli, on STAT1, STAT6, and NFκB is studied using bifurcation analysis. The existence of saddle-node bifurcations in these internal key regulators allows different combinations of steady state levels which are attributable to different fates. Therefore, we propose dynamic bifurcation as a crucial built-in mechanism of macrophage polarization. Next, in order to investigate the polarization of a population of macrophages, bifurcation analysis is employed aligned with agent-based approach and a two-layer model is proposed in which the information from single cells is exploited to model the behavior in tissue level. Also, in this model, a partial differential equation describes the diffusion of secreted cytokines in the medium. Finally, the model was validated against a set of experimental data. Taken together, we have here developed a cell and tissue level model of macrophage polarization behavior which can be used for designing therapeutic interventions.

Soluble ST2 is a biomarker for cardiovascular mortality related to abnormal glucose metabolism in high-risk subjects

AIMS

Inflammation plays a role in the development and progression of type 2 diabetes macroangiopathy. Interleukin 33 (IL-33) drives production of Th2-associated cytokines. The soluble form of suppression of tumorigenicity 2 (sST2) acting as a decoy receptor blocks IL-33 and tones down Th2 inflammatory response. We investigated the role of sST2 as a predictor of CV and all-cause mortality in a cohort of patients affected by established atherosclerotic disease.

METHODS

399 patients with atherosclerotic disease from the Tor Vergata Atherosclerosis Registry performed follow-up every year by phone interview. The primary endpoint was cardiovascular death and the secondary endpoint was death for any other disease.

RESULTS

sST2 plasma levels were significantly increased from normal glucose-tolerant patients to patients with history of type 2 diabetes (p < 0.00001). Levels of sST2 were significantly correlated with fasting plasma glucose (R = 0.16, p = 0.002), HbA1c (R = 0.17, p = 0.002), and HOMA (R = 0.16, p = 0.004). Dividing patients in tertiles of sST2 levels, those belonging to the highest tertile showed an increased rate of all-cause and cardiovascular mortality, (all-cause mortality p = 0.045 and CVD mortality p = 0.02). A multivariate Cox analysis revealed that sST2 increased the risk in cardiovascular mortality per SD by hazard ratio 1.050 (95% CI 1.006-1.097, p = 0.025) after adjustment for age and hs-CRP while it did not significantly change the risk for all-cause mortality.

CONCLUSIONS

High circulating level of sST2 is associated to increased CVD mortality and markers of metabolic dysfunction in subjects with atherosclerotic disease.

Insulin resistance in ischemic stroke

Insulin resistance often refers to a pathological condition in which cells fail to respond to the normal actions of insulin. Increasing literature has noted a critical role of insulin resistance in the pathogenesis of ischemic stroke. Insulin resistance plays an important role in the pathogenesis of ischemic stroke via enhancing advanced changes of atherosclerosis. A variety of literature indicates that insulin resistance enhances platelet adhesion, activation and aggregation which are conducive to the occurrence of ischemic stroke. Insulin resistance also induces hemodynamic disturbances and contributes to the onset of ischemic stroke. In addition, insulin resistance may augment the role of the modifiable risk factors in ischemic stroke and induce the occurrence of ischemic stroke. Preclinical and clinical studies have supported that improving insulin resistance may be an effective measure to prevent or delay ischemic stroke.

MicroRNAs in dysfunctional adipose tissue: cardiovascular implications

In this review, we focus on the emerging role of microRNAs, non-coding RNAs that regulate gene expression and signaling pathways, in dysfunctional adipose tissue. We highlight current paradigms of microRNAs involved in adipose differentiation and function in depots such as white, brown, and beige adipose tissues and potential implications of microRNA dysregulation in human disease such as obesity, inflammation, microvasculature dysfunction, and related cardiovascular diseases. We highlight accumulating studies indicating that adipocyte-derived microRNAs may not only serve as biomarkers of cardiometabolic disease, but also may directly regulate gene expression of other tissues. Finally, we discuss the future prospects, challenges, and emerging strategies for microRNA delivery and targeting for therapeutic applications in cardiovascular disease states associated with adipocyte dysfunction.

Emerging Roles for MicroRNAs in Diabetic Microvascular Disease: Novel Targets for Therapy

Chronic, low-grade systemic inflammation and impaired microvascular function are critical hallmarks in the development of insulin resistance. Accordingly, insulin resistance is a major risk factor for type 2 diabetes and cardiovascular disease. Accumulating studies demonstrate that restoration of impaired function of the diabetic macro- and microvasculature may ameliorate a range of cardiovascular disease states and diabetes-associated complications. In this review, we focus on the emerging role of microRNAs (miRNAs), noncoding RNAs that fine-tune target gene expression and signaling pathways, in insulin-responsive tissues and cell types important for maintaining optimal vascular homeostasis and preventing the sequelae of diabetes-induced end organ injury. We highlight current pathophysiological paradigms of miRNAs and their targets involved in regulating the diabetic microvasculature in a range of diabetes-associated complications such as retinopathy, nephropathy, wound healing, and myocardial injury. We provide an update of the potential use of circulating miRNAs diagnostically in type I or type II diabetes. Finally, we discuss emerging delivery platforms for manipulating miRNA expression or function as the next frontier in therapeutic intervention to improve diabetes-associated microvascular dysfunction and its attendant clinical consequences.

Immunomodulatory effects of adipose tissue-derived stem cells on elastin scaffold remodeling in diabetes

Diabetes is a major risk factor for the progression of vascular disease, contributing to elevated levels of glycoxidation, chronic inflammation and calcification. Tissue engineering emerges as a potential solution for the treatment of vascular diseases however there is a considerable gap in the understanding of how scaffolds and stem cells will perform in patients with diabetes. We hypothesized that adipose tissue-derived stem cells (ASCs) by virtue of their immunosuppressive potential would moderate the diabetes-intensified inflammatory reactions and induce positive construct remodeling. To test this hypothesis, we prepared arterial elastin scaffolds seeded with autologous ASCs and implanted them subdermally in diabetic rats and compared inflammatory markers, macrophage polarization, matrix remodeling, calcification and bone protein expression to control scaffolds implanted with and without cells in nondiabetic rats. ASC-seeded scaffolds exhibited lower levels of CD8+ T-cells and CD68+ pan-macrophages and higher numbers of M2 macrophages, smooth muscle cell-like and fibroblast-like cells. Calcification and osteogenic markers were reduced in ASCseeded scaffolds implanted in non-diabetic rats but remained unchanged in diabetes, unless the scaffolds were first pre-treated with penta-galloyl glucose (PGG), a known anti-oxidative elastin-binding polyphenol. In conclusion, autologous ASC seeding in elastin scaffolds is effective in combating diabetes-related complications. To prevent calcification, the oxidative milieu needs to be reduced by elastin-binding antioxidants such as PGG.

Ankle-brachial index and incident diabetes mellitus: the atherosclerosis risk in communities (ARIC) study

Background

Individuals with peripheral artery disease (PAD) often have reduced physical activity, which may increase the future risk of diabetes mellitus. Although diabetes is a risk factor for PAD, whether low ankle-brachial index (ABI) predates diabetes has not been studied.

Methods

We examined the association of ABI with incident diabetes using Cox proportional hazards models in the ARIC Study. ABI was measured in 12,247 black and white participants without prevalent diabetes at baseline (1987–1989). Incident diabetes cases were identified by blood glucose levels at three subsequent visits (1990–92, 1993–95, and 1996–98) or self-reported physician diagnosis or medication use at those visits or during annual phone interview afterward through 2011.

Results

A total of 3305 participants developed diabetes during a median of 21 years of follow-up. Participants with low (≤0.90) and borderline low (0.91–1.00) ABI had 30–40% higher risk of future diabetes as compared to those with ABI of 1.10–1.20 in the demographically adjusted model. The associations were attenuated after further adjustment for other potential confounders but remained significant for ABI 0.91–1.00 (HR = 1.17, 95% CI 1.04–1.31) and marginally significant for ABI ≤ 0.90 (HR = 1.19, 0.99–1.43). Although the association was largely consistent across subgroups, a stronger association was seen in participants without hypertension, those with normal fasting glucose, and those with a history of stroke compared to their counterparts.

Conclusions

Low ABI was modestly but independently associated with increased risk of incident diabetes in the general population. Clinical attention should be paid to the glucose trajectory among people with low ABI but without diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0476-4) contains supplementary material, which is available to authorized users.

Insulin Resistance Is a Risk Factor for Silent Lacunar Infarction

Background and Purpose—

This study aims to investigate the association between insulin resistance (IR) and silent lacunar infarction (SLI) in healthy adults.

Methods—

We recruited 2326 healthy Korean adults who took health checkups, including a brain magnetic resonance imaging. SLI was defined as an infarction measuring 0.3 to 1.5 cm in diameter that was localized in the territory of perforating branches of cerebral arteries, as seen in the brain magnetic resonance imaging. The homeostasis model assessment–estimated insulin resistance index was used for IR estimation, and the cutoff value for its diagnosis for Koreans was 2.56.

Results—

The mean age of the study population was 56.2 years (range, 40–79 years), and 1279 subjects (55.0%) were male. The prevalence of SLI and IR was 8.1% and 18.1%, respectively. In multivariate logistic analysis, after adjusting for traditional SLI-associated risk factors, IR was positively associated with the prevalence of SLI (adjusted odds ratio, 1.69; 95% confidence interval, 1.16–2.46). The proportion of subjects with multiple SLI lesions (≥2) was also higher in the IR (+) group than that in the IR (−) group (4.3% versus 1.7%; P <0.001). In ordered logistic regression, IR was positively associated with an increase in SLI severity (adjusted odds ratio, 1.76; 95% confidence interval, 1.21–2.56).

Conclusions—

IR is an independent risk factor of SLI presence and its severity in Koreans. Whether improvement of IR might prevent SLI occurrence needs to be addressed by clinical trials.

TCF7L2 polymorphism is associated with low nitric oxide release, endothelial dysfunction and enhanced inflammatory response after myocardial infarction

Backgound

The favorable effects of insulin during myocardial infarction (MI) remain unclear due to the divergence between mechanistic studies and clinical trials of exogenous insulin administration. The rs7903146 polymorphism of the transcription factor 7-like 2 (TCF7L2) gene is associated with attenuated insulin secretion.

Methods

In non-diabetic patients with ST-elevation MI (STEMI), using such a model of genetically determined down-regulation of endogenous insulin secretion we investigated the change in plasma insulin, C-peptide, interleukin-2 (IL-2), C-reactive protein (CRP), and nitric oxide (NOx) levels between admission (D1) and the fifth day after MI (D5). Coronary angiography and flow-mediated dilation (FMD) were performed at admission and 30 days after MI, respectively. Homeostasis Model Assessment estimated insulin secretion (HOMA2%β) and insulin sensitivity (HOMA2%S).

Results

Although glycemia did not differ between genotypes, carriers of the T-allele had lower HOMA2%β and higher HOMA2%S at both D1 and D5. As compared with non-carriers, T-allele carriers had higher plasma IL-2 and CRP at D5, higher intracoronary thrombus grade, lower FMD and NOx change between D1 and D5 and higher 30-day mortality.

Conclusion

In non-diabetic STEMI patients, the rs7903146 TCF7L2 gene polymorphism is associated with lower insulin secretion, worse endothelial function, higher coronary thrombotic burden, and higher short-term mortality.

General significance

During the acute phase of MI, a lower capacity of insulin secretion may influence clinical outcome.

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TCF7L2 rs7903146 polymorphism is associated to lower insulin secretion after STEMI.

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Individuals associated to lower insulin levels had reduced inflammatory markers.

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Lower insulin is associated to high thrombotic burden and endothelial dysfunction.

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TCF7L2 rs7903146 polymorphism is associated to increased mortality 30 days after STEMI.

A Simple Method for Optimization of Reference Gene Identification and Normalization in DNA Microarray Analysis

Background

Comparative DNA microarray analyses typically yield very large gene expression data sets that reflect complex patterns of change. Despite the wealth of information that is obtained, the identification of stable reference genes is required for normalization of disease- or drug-induced changes across tested groups. This is a prerequisite in quantitative real-time reverse transcription-PCR (qRT-PCR) and relative RT-PCR but rare in gene microarray analysis. The goal of the present study was to outline a simple method for identification of reliable reference genes derived from DNA microarray data sets by comparative statistical analysis of software-generated and manually calculated candidate genes.

Material/Methods

DNA microarray data sets derived from whole-blood samples obtained from 14 Zucker diabetic fatty (ZDF) rats (7 lean and 7 diabetic obese) were used for the method development. This involved the use of software-generated filtering parameters to accomplish the desired signal-to-noise ratios, 75^th percentile signal manual normalizations, and the selection of reference genes as endogenous controls for target gene expression normalization.

Results

The combination of software-generated and manual normalization methods yielded a group of 5 stably expressed, suitable endogenous control genes which can be used in further target gene expression determinations in whole blood of ZDF rats.

Conclusions

This method can be used to correct for potentially false results and aid in the selection of suitable endogenous control genes. It is especially useful when aimed to aid the software in cases of borderline results, where the expression and/or the fold change values are just beyond the pre-established set of acceptable parameters.

Chronic Inhibition of PDE5 Limits Pro-Inflammatory Monocyte-Macrophage Polarization in Streptozotocin-Induced Diabetic Mice

Diabetes mellitus is characterized by changes in endothelial cells that alter monocyte recruitment, increase classic (M1-type) tissue macrophage infiltration and lead to self-sustained inflammation. Our and other groups recently showed that chronic inhibition of phosphodiesterase-5 (PDE5i) affects circulating cytokine levels in patients with diabetes; whether PDE5i also affects circulating monocytes and tissue inflammatory cell infiltration remains to be established. Using murine streptozotocin (STZ)-induced diabetes and in human vitro cell-cell adhesion models we show that chronic hyperglycemia induces changes in myeloid and endothelial cells that alter monocyte recruitment and lead to self-sustained inflammation. Continuous PDE5i with sildenafil (SILD) expanded tissue anti-inflammatory TIE2-expressing monocytes (TEMs), which are known to limit inflammation and promote tissue repair. Specifically, SILD: 1) normalizes the frequency of circulating pro-inflammatory monocytes triggered by hyperglycemia (53.7 ± 7.9% of CD11b⁺Gr-1⁺ cells in STZ vs. 30.4 ± 8.3% in STZ+SILD and 27.1 ± 1.6% in CTRL, P<0.01); 2) prevents STZ-induced tissue inflammatory infiltration (4-fold increase in F4/80+ macrophages in diabetic vs. control mice) by increasing renal and heart anti-inflammatory TEMs (30.9 ± 3.6% in STZ+SILD vs. 6.9 ± 2.7% in STZ, P <0.01, and 11.6 ± 2.9% in CTRL mice); 3) reduces vascular inflammatory proteins (iNOS, COX2, VCAM-1) promoting tissue protection; 4) lowers monocyte adhesion to human endothelial cells in vitro through the TIE2 receptor. All these changes occurred independently from changes of glycemic status. In summary, we demonstrate that circulating renal and cardiac TEMs are defective in chronic hyperglycemia and that SILD normalizes their levels by facilitating the shift from classic (M1-like) to alternative (M2-like)/TEM macrophage polarization. Restoration of tissue TEMs with PDE5i could represent an additional pharmacological tool to prevent end-organ diabetic complications.

Methodological and metabolic considerations in the study of caffeine-containing energy drinks

Caffeine-containing energy drinks are popular and widely available beverages. Despite large increases in consumption, studies documenting the nutritional, metabolic, and health implications of these beverages are limited. This review provides some important methodological considerations in the examination of these drinks and highlights their potential impact on the gastrointestinal system, liver, and metabolic health. The gastrointestinal system is important as it comes into contact with the highest concentration of energy drink ingredients and initiates a chain of events to communicate with peripheral tissues. Although energy drinks have diverse compositions, including taurine, ginseng, and carnitine, the most metabolically deleterious ingredients appear to be simple sugars (such as glucose and fructose) and caffeine. In combination, these last two ingredients have the greatest metabolic impact and potential influence on overall health.

Performance effects and metabolic consequences of caffeine and caffeinated energy drink consumption on glucose disposal

This review documents two opposing effects of caffeine and caffeine-containing energy drinks, i.e., their positive effects on athletic performance and their negative impacts on glucose tolerance in the sedentary state. Analysis of studies examining caffeine administration prior to performance-based exercise showed caffeine improved completion time by 3.6%. Similar analyses following consumption of caffeine-containing energy drinks yielded positive, but more varied, benefits, which were likely due to the diverse nature of the studies performed, the highly variable composition of the beverages consumed, and the range of caffeine doses administered. Conversely, analyses of studies administering caffeine prior to either an oral glucose tolerance test or insulin clamp showed a decline in whole-body glucose disposal of ~30%. The consequences of this resistance are unknown, but there may be implications for the development of a number of chronic diseases. Both caffeine-induced performance enhancement and insulin resistance converge with the primary actions of caffeine on skeletal muscle.

Serum advanced glycation end products are associated with insulin resistance in male nondiabetic patients with obstructive sleep apnea

PURPOSE

Advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic vascular complications. Recently, growing evidence has shown that AGEs could be involved in the pathogenesis of insulin resistance. It has also been suggested that circulating AGE are associated with insulin resistance in nondiabetic patients. This study investigated whether serum AGEs levels are associated with insulin resistance in nondiabetic patients with obstructive sleep apnea (OSA).

METHODS

A total of 139 male nondiabetic patients with OSA were recruited for participation in the study. Serum AGE levels were examined using an enzyme-linked immunosorbent assay. Insulin resistance was determined using the homeostasis model assessment index (HOMA-IR).

RESULTS

There was a significant correlation between serum AGEs and the apnea-hypopnea index (AHI) (r = 0.281, p = 0.014), duration of SaO₂ < 90% (r = 0.267, p = 0.018), minimum SaO₂ (r = -0.188, p = 0.046), high-sensitivity C-reactive protein (hsCRP) (r = 0.274, p = 0.012), and HOMA-IR (r = 0.303, p < 0.001). Multiple regression analysis showed that serum AGEs (p = 0.011), AHI (p = 0.024), waist circumference (p = 0.040), and hsCRP (p = 0.046) were independently associated with HOMA-IR (R(2) = 0.392). In addition, the strength of the correlation between serum AGEs and HOMA-IR was related to the severity of OSA.

CONCLUSIONS

The present study indicated that serum AGE levels were associated with insulin resistance in male nondiabetic patients with OSA. These findings suggest that AGEs may play a role in insulin resistance in OSA and may also be a biomarker for patients with OSA with high risk of developing type 2 diabetes.

Diabetes, Endothelial Dysfunction, and Vascular Repair: What Should a Diabetologist Keep His Eye on?

Cardiovascular complications are the most common complications of diabetes mellitus. A prominent attribute of diabetic cardiovascular complications is accelerated atherosclerosis, considered as a still incurable disease, at least at more advanced stages. The discovery of endothelial progenitor cells (EPCs), able to replace old and injured mature endothelial cells and capable of differentiating into healthy and functional endothelial cells, has offered the prospect of merging the traditional theories on the pathogenesis of atherosclerosis with evolving concepts of vascular biology. The literature supports the notion that EPC alterations are involved in the pathogenesis of vascular diseases in diabetics, but at present many questions remain unanswered. In this review the aspects linking endothelial progenitor cells to the altered vascular biology in diabetes mellitus are discussed.

Gal-geun-dang-gwi-tang improves diabetic vascular complication in apolipoprotein E KO mice fed a western diet

BACKGROUND

Gal-geun-dang-gwi-tang (GGDGT), an herbal medicine, is used to treat hypertension, stroke, and other inflammatory disorders in the clinical setting. Recently, GGDGT was recognized by the Korea Institute of Oriental Medicine. This study aimed to evaluate the effects of GGDGT in a diabetic atherosclerosis model using apolipoprotein E knockout (ApoE-/-) mice fed a Western diet.

METHODS

The mice were divided into four groups: control group, C57BL6J mice receiving a regular diet (RD); ApoE-/- group, ApoE-/- mice receiving a Western diet (WD); rosiglitazone group, ApoE-/- mice receiving rosiglitazone (WD + 10 mg · kg(-1) · day(-1)); GGDGT group, ApoE-/- mice receiving GGDGT (WD + 200 mg · kg(-1) · day(-1)).

RESULTS

Treatment with GGDGT significantly improved glucose tolerance and plasma lipid levels. In addition, GGDGT ameliorated acetylcholine-induced vascular relaxation of the aortic rings. Immunohistochemical staining showed that GGDGT suppressed intercellular adhesion molecule (ICAM)-1 expression; however, expression of endothelial nitric oxide synthase (eNOS) and insulin receptor substrate (IRS)-1 were restored in the thoracic aorta and skeletal muscle, respectively.

CONCLUSIONS

These findings suggest that GGDGT attenuates endothelial dysfunction via improvement of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signalling pathway and improves insulin sensitivity in diabetic atherosclerosis.

Inflammation, oxidative stress, and cardiovascular disease risk factors in adults with cystic fibrosis

Cystic fibrosis (CF) represents one of a number of localized lung and non-lung diseases with an intense chronic inflammatory component associated with evidence of systemic oxidative stress. Many of these chronic inflammatory diseases are accompanied by an array of atherosclerotic processes and cardiovascular disease (CVD), another condition strongly related to inflammation and oxidative stress. As a consequence of a dramatic increase in long-lived patients with CF in recent decades, the specter of CVD must be considered in these patients who are now reaching middle age and beyond. Buttressed by recent data documenting that CF patients exhibit evidence of endothelial dysfunction, a recognized precursor of atherosclerosis and CVD, the spectrum of risk factors for CVD in CF is reviewed here. Epidemiological data further characterizing the presence and extent of atherogenic processes in CF patients would seem important to obtain. Such studies should further inform and offer mechanistic insights into how other chronic inflammatory diseases potentiate the processes leading to CVDs.

Cell-intrinsic lysosomal lipolysis is essential for alternative activation of macrophages

Alternative (M2) activation of macrophages driven via the α-chain of the receptor for interleukin 4 (IL-4Rα) is important for immunity to parasites, wound healing, the prevention of atherosclerosis and metabolic homeostasis. M2 polarization is dependent on fatty acid oxidation (FAO), but the source of the fatty acids that support this metabolic program has not been clear. We found that the uptake of triacylglycerol substrates via the scavenger receptor CD36 and their subsequent lipolysis by lysosomal acid lipase (LAL) was important for the engagement of elevated oxidative phosphorylation, enhanced spare respiratory capacity (SRC), prolonged survival and expression of genes that together define M2 activation. Inhibition of lipolysis suppressed M2 activation during infection with a parasitic helminth and blocked protective responses to this pathogen. Our findings delineate a critical role for cell-intrinsic lysosomal lipolysis in M2 activation.

Metabolic syndrome, adiponectin and proinflammatory status in patients with type 1 diabetes mellitus

OBJECTIVES

To assess the prevalence of metabolic syndrome and evaluate proinflammatory status in patients with type 1 diabetes, and to analyse the relationship between inflammation, metabolic control and insulin resistance in these patients.

METHODS

Patients with type 1 diabetes were stratified according to the presence or absence of metabolic syndrome. Serum adiponectin, leptin, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and high-sensitivity C-reactive protein (hsCRP) were quantified.

RESULTS

The prevalence of metabolic syndrome was 28.6% (22/77). Patients with metabolic syndrome had lower adiponectin concentrations and higher leptin, TNF-α, IL-6 and hsCRP concentrations compared with patients without metabolic syndrome. In addition, metabolic syndrome was associated with higher glycosylated haemoglobin and insulin dose, and increased insulin resistance.

CONCLUSIONS

The proinflammatory state associated with metabolic syndrome in patients with type 1 diabetes leads to deterioration of glycaemic control and an increase in the required daily dose of insulin. Early and proactive diagnosis of metabolic syndrome in these patients will allow medication and lifestyle optimization, in order to prevent the occurrence of diabetes complications and improve health-related quality-of-life.

Regulation of insulin resistance and adiponectin signaling in adipose tissue by liver X receptor activation highlights a cross-talk with PPARγ

Liver X receptors (LXRs) have been recognized as a promising therapeutic target for atherosclerosis; however, their role in insulin sensitivity is controversial. Adiponectin plays a unique role in maintaining insulin sensitivity. Currently, no systematic experiments elucidating the role of LXR activation in insulin function based on adiponectin signaling have been reported. Here, we investigated the role of LXR activation in insulin resistance based on adiponectin signaling, and possible mechanisms. C57BL/6 mice maintained on a regular chow received the LXR agonist, T0901317 (30 mg/kg.d) for 3 weeks by intraperitoneal injection, and differentiated 3T3-L1 adipocytes were treated with T0901317 or GW3965. T0901317 treatment induced significant insulin resistance in C57BL/6 mice. It decreased adiponectin gene transcription in epididymal fat, as well as serum adiponectin levels. Activity of AMPK, a key mediator of adiponectin signaling, was also decreased, resulting in decreased Glut-4 membrane translocation in epididymal fat. In contrast, adiponectin activity was not changed in the liver of T0901317 treated mice. In vitro, both T0901317 and GW3965 decreased adiponectin expression in adipocytes in a dose-dependent manner, an effect which was diminished by LXRα silencing. ChIP-qPCR studies demonstrated that T0901317 decreased the binding of PPARγ to the PPAR-responsive element (PPRE) of the adiponectin promoter in a dose-dependent manner. Furthermore, T0901317 exerted an antagonistic effect on the expression of adiponectin in adipocytes co-treated with 3 µM Pioglitazone. In luciferase reporter gene assays, T0901317 dose-dependently inhibited PPRE-Luc activity in HEK293 cells co-transfected with LXRα and PPARγ. These results suggest that LXR activation induces insulin resistance with decreased adiponectin signaling in epididymal fat, probably due to negative regulation of PPARγ signaling. These findings indicate that the potential of LXR activation as a therapeutic target for atherosclerosis may be limited by the possibility of exacerbating insulin resistance-related disease.

Adipose tissue and vascular phenotypic modulation by voluntary physical activity and dietary restriction in obese insulin-resistant OLETF rats

Adipose tissue (AT)-derived cytokines are proposed to contribute to obesity-associated vascular insulin resistance. We tested the hypothesis that voluntary physical activity and diet restriction-induced maintenance of body weight would both result in decreased AT inflammation and concomitant improvements in insulin-stimulated vascular relaxation in the hyperphagic, obese Otsuka Long-Evans Tokushima fatty (OLETF) rat. Rats (aged 12 wk) were randomly assigned to sedentary (SED; n = 10), wheel running (WR; n = 10), or diet restriction (DR; n = 10; fed 70% of SED) for 8 wk. WR and DR rats exhibited markedly lower adiposity (7.1 ± 0.4 and 15.7 ± 1.1% body fat, respectively) relative to SED (27 ± 1.2% body fat), as well as improved blood lipid profiles and systemic markers of insulin resistance. Reduced adiposity in both WR and DR was associated with decreased AT mRNA expression of inflammatory genes (e.g., MCP-1, TNF-α, and IL-6) and markers of immune cell infiltration (e.g., CD8, CD11c, and F4/80). The extent of these effects were most pronounced in visceral AT compared with subcutaneous and periaortic AT. Markers of inflammation in brown AT were upregulated with WR but not DR. In periaortic AT, WR- and DR-induced reductions in expression and secretion of cytokines were accompanied with a more atheroprotective gene expression profile in the adjacent aortic wall. WR, but not DR, resulted in greater insulin-stimulated relaxation in the aorta; an effect that was, in part, mediated by a decrease in insulin-induced endothelin-1 activation in WR aorta. Collectively, we show in OLETF rats that lower adiposity leads to less AT and aortic inflammation, as well as an exercise-specific improvement in insulin-stimulated vasorelaxation.

Differential regulation of adipose tissue and vascular inflammatory gene expression by chronic systemic inhibition of NOS in lean and obese rats

We tested the hypothesis that a decrease in bioavailability of nitric oxide (NO) would result in increased adipose tissue (AT) inflammation. In particular, we utilized the obese Otsuka Long Evans Tokushima Fatty rat model (n = 20) and lean Long Evans Tokushima Otsuka counterparts (n = 20) to determine the extent to which chronic inhibition of NO synthase (NOS) with N (ω) -nitro-l-arginine methyl ester (L-NAME) treatment (for 4 weeks) upregulates expression of inflammatory genes and markers of immune cell infiltration in retroperitoneal white AT, subscapular brown AT, periaortic AT as well as in its contiguous aorta free of perivascular AT. As expected, relative to lean rats (% body fat = 13.5 ± 0.7), obese rats (% body fat = 27.2 ± 0.8) were hyperlipidemic (total cholesterol 77.0 ± 2.1 vs. 101.0 ± 3.3 mg/dL), hyperleptinemic (5.3 ± 0.9 vs. 191.9 ± 59.9 pg/mL), and insulin-resistant (higher HOMA IR index [3.9 ± 0.8 vs. 25.2 ± 4.1]). Obese rats also exhibited increased expression of proinflammatory genes in perivascular, visceral, and brown ATs. L-NAME treatment produced a small but statistically significant decrease in percent body fat (24.6 ± 0.9 vs. 27.2 ± 0.8%) and HOMA IR index (16.9 ± 2.3 vs. 25.2 ± 4.1) in obese rats. Further, contrary to our hypothesis, we found that expression of inflammatory genes in all AT depots examined were generally unaltered with L-NAME treatment in both lean and obese rats. This was in contrast with the observation that L-NAME produced a significant upregulation of inflammatory and proatherogenic genes in the aorta. Collectively, these findings suggest that chronic NOS inhibition alters transcriptional regulation of proinflammatory genes to a greater extent in the aortic wall compared to its adjacent perivascular AT, or visceral white and subscapular brown AT depots.

O-GlcNAcylation and Inflammation: A Vast Territory to Explore

O-GlcNAcylation is a reversible post-translational modification that regulates the activities of cytosolic and nuclear proteins according to glucose availability. This modification appears to participate in several hyperglycemia-associated complications. An important feature of metabolic diseases such as diabetes and obesity is the presence of a low-grade chronic inflammation that causes numerous complications. Hyperglycemia associated with the metabolic syndrome is known to promote inflammatory processes through different mechanisms including oxidative stress and abnormally elevated protein O-GlcNAcylation. However, the role of O-GlcNAcylation on inflammation remains contradictory. O-GlcNAcylation associated with hyperglycemia has been shown to increase nuclear factor κB (NFκB) transcriptional activity through different mechanisms. This could contribute in inflammation-associated diabetic complications. However, in other conditions such as acute vascular injury, O-linked N-acetyl glucosamine (O-GlcNAc) also exerts anti-inflammatory effects via inhibition of the NFκB pathway, suggesting a complex regulation of inflammation by O-GlcNAc. Moreover, whereas macrophages and monocytes exposed to high glucose for a long-term period developed a pro-inflammatory phenotype, the impact of O-GlcNAcylation in these cells remains unclear. A future challenge will be to clearly establish the role of O-GlcNAcylation in pro- and anti-inflammatory functions in macrophages.

Angiosome-targeted revascularisation in diabetic foot ulcers

Peripheral vascular disease is a common complication of type 2 diabetes and is often more severe and diffuse than in non-diabetic individuals with a higher risk of major amputations in the lower limbs. Diabetic foot revascularisation using both traditional bypass surgery and endovascular therapy are often burdened by the failure and the inevitable subsequent massive amputation. In this study, we examined the clinical response of diabetic patients with critical limb ischaemia and extended ischaemic wounds, treated with a new angiosome-based revascularisation technique. In a 3-year period, nine diabetic patients with imminent amputation threatening and foot ulcers with no feasible arterial revascularisation options were treated by the angiosome-based surgical technique by means of deep vein arterialisation. The postoperative tcPO2 evaluation showed a mean increase in the cutaneous oxygen tension in all patients treated. The overall survival rates were 88·88%, 88·88% and 77·77% at 12, 24 and 36 months, respectively. Limb salvage was 100% at 1 year and steady at 88·88% thereafter. Surgical deep venous arterialisation might be considered as an extreme alternative to attempt tissue preservation in limbs unfit for conventional arterial revascularisations. This technique would give advantages to the patients in terms of better compliance to the minor amputations and thus avoiding major limb amputations.