Role of insulin resistance in endothelial dysfunction

Seasonality of Insulin Resistance, Glucose, and Insulin Among Middle-Aged and Elderly Population: The Rotterdam Study

CONTEXT

There are discrepancies in the seasonality of insulin resistance (IR) across the literature, probably due to age-related differences in the seasonality of lifestyle factors and thermoregulation mechanisms.

OBJECTIVE

To estimate the seasonality of IR according to the homeostatic model assessment-IR (HOMA-IR), glucose, and insulin levels and to examine the role of lifestyle markers [body mass index (BMI) and physical activity] and meteorological factors, according to age.

DESIGN, SETTING, AND PARTICIPANTS

Seasonality was examined using cosinor analysis among middle-aged (45 to 65 years) and elderly (≥65 years) participants of a population-based Dutch cohort. We analyzed 13,622 observations from 8979 participants (57.6% women) without diagnosis of diabetes and fasting glucose <7 mmol/L. BMI was measured, physical activity was evaluated using a validated questionnaire, and meteorological factors (daily mean ambient temperature, mean relative humidity, total sunlight hours, and total precipitation) were obtained from local records. Seasonality estimates were adjusted for confounders.

RESULTS

Among the middle-aged participants, seasonal variation estimates were: 0.11 units (95% confidence interval: 0.03, 0.20) for HOMA-IR, 0.28 µIU/mL (-0.05, 0.69) for insulin, and 0.05 mmol/L (0.01, 0.09) for glucose. These had a summer peak, and lifestyle markers explained the pattern. Among the elderly, seasonal variations were: 0.29 units (0.21, 0.37) for HOMA-IR, 0.96 µIU/mL (0.58, 1.28) for insulin, and 0.01 mmol/L (-0.01, 0.05) for glucose. These had a winter peak and ambient temperature explained the pattern.

CONCLUSION

Impaired thermoregulation mechanisms could explain the winter peak of IR among elderly people without diabetes. The seasonality of lifestyle factors may explain the seasonality of glucose.

The Effect of Soluble Fiber Supplementation on Metabolic Syndrome Profile among Newly Diagnosed Type 2 Diabetes Patients

Diets with high fiber content improve most metabolic syndrome (MetS) profile in non-diabetic individuals, but there is scarce information about the role of fiber intake in patients with the MetS and diabetes. The objective of this study is to determine whether soluble fiber supplementation improve MetS profile for 8 weeks of intervention in newly diagnosed type 2 diabetes (T2D) adult patients. After one week of dietary stabilization phase, 36 newly diagnosed T2D patients were stratified to different strata according to sex, age, fasting blood sugar (FBS), and waist circumference (WC). Then they were randomly allocated into 2 groups. The psyllium group (n = 18) received 10.5 g of psyllium daily for 8 weeks. The control group (n = 18) maintained their regular diet for 8 weeks. Soluble fiber supplementation showed significant reduction in the majority of MetS profile; FBS (43.55 mg/dL, p < 0.001), triglyceride (37.89 mg/dL, p < 0.001), total cholesterol (20.32 mg/dL, p < 0.001), systolic blood pressure (7.50 mmHg, p < 0.001), diastolic blood pressure (2.78 mmHg, p = 0.013), and WC (2.54 cm, p < 0.001) in the intervention group compared with the control group after 8 weeks of intervention. The high-density lipoprotein cholesterol was reduced in both groups, but this reduction was insignificant. The improvement in the MetS profile was enhanced by combining psyllium to the normal diet. Consumption of foods containing moderate amounts of these fibers may improve MetS profile in newly diagnosed T2D patients. This study was registered in Current Controlled Trials (PHRC/HC/28/15).

Swimming, but not vitamin E, ameliorates prothrombotic state and hypofibrinolysis in a rat model of nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with a systemic procoagulant hypofibrinolysis state that is considered as a risk factor for microangiopathy and peripheral vascular diseases. Swimming exercise ameliorates the metabolic dysfunction in type 2 diabetes. Vitamin E is a natural antioxidant that reduces the risk of endothelial dysfunction in metabolic syndrome. The aim of the present study is to investigate the effect of combined swimming exercise with vitamin E on coagulation as well as blood fibrinolysis markers in rats with NAFLD.

METHODS

Eighty male rats were divided into control, control+vitamin E, control+exercise, high-fat diet (HFD), HFD+vitamin E, HFD+exercise, and HFD+vitamin E+exercise groups. Glucose, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), triglycerides, cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL), alanine transaminase (ALT) and aspartate transaminase (AST), intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1), endothelin-1, von Willebrand factor (vWF), fibrinogen, plasminogen activator inhibitor (PAI-1), fibrin degradation products (FDP), platelet count and aggregation, bleeding and clotting times, activated partial thromboplastin time (aPTT), and prothrombin time (PT) were determined.

RESULTS

HFD increased lipid profile, insulin, glucose, HOMA-IR, liver enzymes, adhesion molecules, endothelin-1, vWF, platelet aggregation, fibrinogen, FDP, and PAI-1, and decreased clotting and bleeding times and HDL. Although exercise reduced lipid profile, glucose, insulin, HOMA-IR, vWF, platelet aggregation, fibrinogen, FDP, and PAI-1 and increased PT, aPTT, bleeding and clotting times, and HDL, vitamin E had no effect.

CONCLUSIONS

Exercise, but not vitamin E, ameliorated the HFD-induced prothrombotic state and enhanced fibrinolytic activity.

Replacing carbohydrate during a glucose challenge with the egg white portion or whole eggs protects against postprandial impairments in vascular endothelial function in prediabetic men by limiting increases in glycaemia and lipid peroxidation

Eggs attenuate postprandial hyperglycaemia (PPH), which transiently impairs vascular endothelial function (VEF). We hypothesised that co-ingestion of a glucose challenge with egg-based meals would protect against glucose-induced impairments in VEF by attenuating PPH and oxidative stress. A randomised, cross-over study was conducted in prediabetic men (n20) who ingested isoenegertic meals (1674 kJ (400 kcal)) containing 100 g glucose (GLU), or 75 g glucose with 1·5 whole eggs (EGG), seven egg whites (WHITE) or two egg yolks (YOLK). At 30 min intervals for 3 h, brachial artery flow-mediated dilation (FMD), plasma glucose, insulin, cholecystokinin (CCK), lipids (total, LDL- and HDL-cholesterol; TAG), F2-isoprostanes normalised to arachidonic acid (F2-IsoPs/AA), and methylglyoxal were assessed. In GLU, FMD decreased at 30–60 min and returned to baseline levels by 90 min. GLU-mediated decreases in FMD were attenuated at 30–60 min in EGG and WHITE. Compared with GLU, FMDAUCwas higher in EGG and WHITE only. Relative to baseline, glucose increased at 30–120 min in GLU and YOLK but only at 30–90 min in EGG and WHITE. GlucoseAUCand insulinAUCwere also lower in EGG and WHITE only. However, CCKAUCwas higher in EGG and WHITE compared with GLU. Compared with GLU, F2-IsoPs/AAAUCwas lower in EGG and WHITE but unaffected by YOLK. Postprandial lipids and methylglyoxal did not differ between treatments. Thus, replacing a portion of a glucose challenge with whole eggs or egg whites, but not yolks, limits postprandial impairments in VEF by attenuating increases in glycaemia and lipid peroxidation.

Uric Acid Impairs Insulin Signaling by Promoting Enpp1 Binding to Insulin Receptor in Human Umbilical Vein Endothelial Cells

High levels of uric acid (UA) are associated with type-2 diabetes and cardiovascular disease. Recent pieces of evidence attributed to UA a causative role in the appearance of diabetes and vascular damage. However, the molecular mechanisms by which UA induces these alterations have not been completely elucidated so far. Among the mechanisms underlying insulin resistance, it was reported the role of a transmembrane glycoprotein, named either ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) or plasma cell antigen 1, which is able to inhibit the function of insulin receptor (I_R) and it is overexpressed in insulin-resistant subjects. In keeping with this, we stimulated human umbilical vein endothelial cells (HUVECs) with insulin and UA to investigate the effects of UA on insulin signaling pathway, testing the hypothesis that UA can interfere with insulin signaling by the activation of ENPP1. Cultures of HUVECs were stimulated with insulin, UA and the urate transporter SLC22A12 (URAT1) inhibitor probenecid. Akt and endothelial nitric oxide synthase (eNOS) phosphorylation levels were investigated by immunoblotting. ENPP1 binding to I_R and its tyrosine phosphorylation levels were tested by immunoprecipitation and immunoblotting. UA inhibited insulin-induced Akt/eNOS axis. Moreover, UA induced ENPP1 binding to I_R that resulted in an impairment of insulin signaling cascade. Probenecid reverted UA effects, suggesting that UA intracellular uptake is required for its action. In endothelial cells, UA directly interferes with insulin signaling pathway at receptor level, through ENPP1 recruitment. This evidence suggests a new molecular model of UA-induced insulin resistance and vascular damage.

Role of disturbed fatty acids metabolism in the pathophysiology of diabetic erectile dysfunction

BACKGROUND

Vasculogenic erectile dysfunction (VED) is considered as a common complication among people with type 2 diabetes (T2D). We tested whether changes in fatty acid (FAs) classes measured in erythrocytes are associated with increased risk of diabetic VED along with related risk factors.

METHODS

We assessed erythrocyte FAs composition, lipid peroxidation parameters and inflammatory cytokines among 72 T2D men with VED, 78 T2D men without VED and 88 healthy volunteers with similar age. Biochemical, hepatic, lipid and hormonal profiles were measured.

RESULTS

T2D people with VED had significant decrease in the indexes of Δ6-desaturase and elongase activities compared to the other studied groups. The same group of participants displayed lower erythrocytes levels of dihomo-γ-linolenic acid (C20:3n-6) (P < .001), precursor of the messenger molecule PGE1 mainly involved in promoting erection. Moreover, absolute SFAs concentration and HOMA IR levels were higher in T2D people with VED when compared to controls and associated with impaired NO concentration (1.43 vs 3.30 ng/L, P < .001). Our results showed that IL-6 and TNF-α were significantly increased and positively correlated with MDA levels only in T2D people with VED (r = 0.884, P = .016 and r = 0.753, P = .035; respectively) suggesting a decrease in the relative availability of vasodilator mediators and an activation of vasoconstrictors release.

CONCLUSION

Our findings show that the deranged FAs metabolism represents a potential marker of VED in progress, or at least an indicator of increased risk within men with T2D.

Insulin Resistance in Kidney Disease: Is There a Distinct Role Separate from That of Diabetes or Obesity?

Insulin resistance is a central component of the metabolic dysregulation observed in obesity, which puts one at risk for the development of type 2 diabetes and complications related to diabetes such as chronic kidney disease. Insulin resistance and compensatory hyperinsulinemia place one at risk for other risk factors such as dyslipidemia, hypertension, and proteinuria, e.g., development of kidney disease. Our traditional view of insulin actions focuses on insulin-sensitive tissues such as skeletal muscle, liver, adipose tissue, and the pancreas. However, insulin also has distinct actions in kidney tissue that regulate growth, hypertrophy, as well as microcirculatory and fibrotic pathways which, in turn, impact glomerular filtration, including that governed by tubuloglomerular feedback. However, it is often difficult to discern the distinct effects of excess circulating insulin and impaired insulin actions, as exist in the insulin resistance individual, from the associated effects of obesity or elevated systolic blood pressure on the development and progression of kidney disease over time. Therefore, we review the experimental and clinical evidence for the distinct impact of insulin resistance on kidney function and disease.

Cellular mechanisms underlying obesity-induced arterial stiffness

Obesity is an emerging pandemic driven by consumption of a diet rich in fat and highly refined carbohydrates (a Western diet) and a sedentary lifestyle in both children and adults. There is mounting evidence that arterial stiffness in obesity is an independent and strong predictor of cardiovascular disease (CVD), cognitive functional decline, and chronic kidney disease. Cardiovascular stiffness is a precursor to atherosclerosis, systolic hypertension, cardiac diastolic dysfunction, and impairment of coronary and cerebral flow. Moreover, premenopausal women lose the CVD protection normally afforded to them in the setting of obesity, insulin resistance, and diabetes, and this loss of CVD protection is inextricably linked to an increased propensity for arterial stiffness. Stiffness of endothelial and vascular smooth muscle cells, extracellular matrix remodeling, perivascular adipose tissue inflammation, and immune cell dysfunction contribute to the development of arterial stiffness in obesity. Enhanced endothelial cortical stiffness decreases endothelial generation of nitric oxide, and increased oxidative stress promotes destruction of nitric oxide. Our research over the past 5 years has underscored an important role of increased aldosterone and vascular mineralocorticoid receptor activation in driving development of cardiovascular stiffness, especially in females consuming a Western diet. In this review the cellular mechanisms of obesity-associated arterial stiffness are highlighted.

Diffuse Dermal Angiomatosis of the Breast: A Distinct Entity in the Spectrum of Cutaneous Reactive Angiomatoses - Clinicopathologic Study of Two Cases and Comprehensive Review of the Literature

Diffuse dermal angiomatosis (DDA) is a rare reactive angioproliferation in the skin and considered to be a subtype in the group of cutaneous reactive angiomatoses. DDA is clinically characterized by livedoid patches and plaques with tender ulceration. Its histologic features are a reactive diffuse proliferation of bland endothelial cells and pericytes within the dermis, forming small capillary vessels. Previously described cases of DDA most commonly involved the limbs and were associated with a wide spectrum of predisposing comorbidities, especially advanced atherosclerotic vascular disease and arteriovenous fistula. However, several cases of DDA of the breast (DDAB) have been reported in recent years. In this study we present 2 additional patients with DDAB and review all 36 cases of DDAB published in the literature. We describe the clinical and histopathologic characteristics, hypothesized pathogenetic mechanisms, and predisposing conditions of this rare skin disorder and discuss treatment options. The breast is a more commonly involved site of DDA than previously believed. DDAB typically occurs in middle-aged women and is associated with macromastia, overweight or obesity, and probably smoking. Predisposing comorbid conditions differ from those of DDA involving other parts of the body, making DDAB a unique clinicopathologic entity in the spectrum of cutaneous reactive angiomatoses. Currently there is no consensus on the best therapeutic approach. Isotretinoin and other medical therapies have been used with limited success. Breast reduction surgery appears to be a viable treatment option for DDAB in women with macromastia and might provide definitive healing.

Metformin Improves Endothelial Function and Reduces Blood Pressure in Diabetic Spontaneously Hypertensive Rats Independent from Glycemia Control: Comparison to Vildagliptin

Metformin confers vascular benefits beyond glycemia control, possibly via pleiotropic effects on endothelial function. In type-1-diabetes-mellitus (T1DM-)patients metformin improved flow-mediated dilation but also increased prostaglandin(PG)-F_2α, a known endothelial-contracting factor. To explain this paradoxical finding we hypothesized that metformin increased endothelial-vasodilator mediators (e.g. NO and EDHF) to an even larger extent. Spontaneously-hypertensive-rats (SHR) display impaired endothelium-dependent relaxation (EDR) involving contractile PGs. EDR was studied in isolated SHR aortas and the involvement of PGs, NO and EDHF assessed. 12-week metformin 300 mg/kg/day improved EDR by up-regulation of NO and particularly EDHF; it also reduced blood pressure and increased plasma sulphide levels (a proxy for H₂S, a possible mediator of EDHF). These effects persisted in SHR with streptozotocin (STZ)-induced T1DM. Vildagliptin (10 mg/kg/day), targeting the incretin axis by increasing GLP-1, also reduced blood pressure and improved EDR in SHR aortas, mainly via the inhibition of contractile PGs, but not in STZ-SHR. Neither metformin nor vildagliptin altered blood glucose or HbA_1c. In conclusion, metformin reduced blood pressure and improved EDR in SHR aorta via up-regulation of NO and particularly EDHF, an effect that was independent from glycemia control and maintained during T1DM. A comparison to vildagliptin did not support effects of metformin mediated by GLP-1.

Pulmonary vascular effect of insulin in a rodent model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is associated with metabolic derangements including insulin resistance, although their effects on the cardiopulmonary disease are unclear. We hypothesized that insulin resistance promotes pulmonary hypertension (PH) development and mutations in type 2 bone morphogenetic protein receptor (BMPR2) cause cellular insulin resistance. Using a BMPR2 transgenic murine model of PAH and two models of inducible diabetes mellitus, we explored the impact of hyperglycemia and/or hyperinsulinemia on development and severity of PH. We assessed insulin signaling and insulin-mediated glucose uptake in human endothelial cells with and without mutations in BMPR2. PH developed in control mice fed a Western diet and PH in BMPR2 mutant mice was increased by Western diet. Pulmonary artery pressure correlated strongly with fasting plasma insulin but not glucose. Reactive oxygen species were increased in lungs of insulin-resistant animals. BMPR2 mutation impaired insulin-mediated endothelial glucose uptake via reduced glucose transporter translocation despite intact insulin signaling. Experimental hyperinsulinemia is strongly associated with PH in both control and BMPR2-mutant mice, though to a greater degree in those with BMPR2 mutation. Human pulmonary endothelial cells with BMPR2 mutation have evidence of reduced glucose uptake due to impaired glucose transporter translocation. These experiments support a role for hyperinsulinemia in pulmonary vascular disease.

Sedentary Behavior and Cardiovascular Disease Risk: Mediating Mechanisms

Sedentary behavior has a strong association with cardiovascular disease (CVD) risk, which may be independent of physical activity. To date, the mechanism(s) that mediate this relationship are poorly understood. We hypothesize that sedentary behavior modifies key hemodynamic, inflammatory, and metabolic processes resulting in impaired arterial health. Subsequently, these vascular impairments directly and indirectly contribute to the development of CVD.

Obesity, metabolic syndrome and diabetic retinopathy: Beyond hyperglycemia

Diabetic retinopathy (DR) is the most feared ocular manifestation of diabetes. DR is characterized by progressive retinal damage that may eventually result in blindness. Clinically, this blindness is caused by progressive damage to the retinal microvasculature, which leads to ischemia, retinal swelling, and neovascularization. Retinopathy is associated with both type 1 and type 2 diabetes, with DR being the leading cause of new onset blindness in United States adults. Despite this strong association with diabetes, it must be noted that the development of retinopathy lesions is multifactorial and may occur in individuals without an established history of diabetes. Metabolic syndrome is a multifactorial condition of central obesity, hypertriglyceridemia, dyslipidemia, hypertension, fasting hyperglycemia, and insulin resistance. Although several studies examined the individual components observed in the metabolic syndrome in relation to the development of DR, there is conflicting data as to the association of the metabolic syndrome with the development of retinopathy lesions in non-diabetic subjects. This review will summarize the current literature on the evidence of the metabolic syndrome on retinopathy in subjects with and without an established history of diabetes. This review will also discuss some of the mechanisms through which metabolic syndrome can contribute to the development of retinopathy.

Oxidative and inflammatory signals in obesity-associated vascular abnormalities

Obesity is associated with increased cardiovascular morbidity and mortality in part due to vascular abnormalities such as endothelial dysfunction and arterial stiffening. The hypertension and other health complications that arise from these vascular defects increase the risk of heart diseases and stroke. Prooxidant and proinflammatory signaling pathways as well as adipocyte-derived factors have emerged as critical mediators of obesity-associated vascular abnormalities. Designing treatments aimed specifically at improving the vascular dysfunction caused by obesity may provide an effective therapeutic approach to prevent the cardiovascular sequelae associated with excessive adiposity. In this review, we discuss the recent evidence supporting the role of oxidative stress and cytokines and inflammatory signals within the vasculature as well as the impact of the surrounding perivascular adipose tissue (PVAT) on the regulation of vascular function and arterial stiffening in obesity. In particular, we focus on the highly plastic nature of the vasculature in response to altered oxidant and inflammatory signaling and highlight how weight management can be an effective therapeutic approach to reduce the oxidative stress and inflammatory signaling and improve vascular function.

Effects of Sugar-Sweetened Beverage Consumption on Microvascular and Macrovascular Function in a Healthy Population

Objective—

To assess vascular function during acute hyperglycemia induced by commercial sugar-sweetened beverage (SSB) consumption and its effect on underlying mechanisms of the nitric oxide pathway.

Approach and Results—

In a randomized, single-blind, crossover trial, 12 healthy male participants consumed 600 mL (20 oz.) of water or a commercial SSB across 2 visits. Endothelial and vascular smooth muscle functions were assessed in the microcirculation using laser speckle contrast imaging coupled with iontophoresis and in the macrocirculation using brachial artery ultrasound with flow- and nitrate-mediated dilation. Compared with water, SSB consumption impaired microvascular and macrovascular endothelial function as indicated by a decrease in the vascular response to acetylcholine iontophoresis (208.3±24.3 versus 144.2±15.7%, P <0.01) and reduced flow-mediated dilation (0.019±0.002 versus 0.014±0.002%/s, P <0.01), respectively. Systemic vascular smooth muscle remained preserved. Similar decreases in endothelial function were observed during acute hyperglycemia in an in vivo rat model. However, function was fully restored by treatment with the antioxidants, N -acetylcysteine and apocynin. In addition, ex vivo experiments revealed that although the production of reactive oxygen species was increased during acute hyperglycemia, the bioavailability of nitric oxide in the endothelium was decreased, despite no change in the activation state of endothelial nitric oxide synthase.

Conclusions—

To our knowledge, this is the first study to assess the vascular effects of acute hyperglycemia induced by commercial SSB consumption alone. These findings suggest that SSB-mediated endothelial dysfunction is partly due to increased oxidative stress that decreases nitric oxide bioavailability.

Clinical Trial Registration—

URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=366442&isReview=true . Australian New Zealand Clinical Trials Registry Number: ACTRN12614000614695.

Metabolic Syndrome in Long-Term Survivors of Hematopoietic Stem-Cell Transplantation

Since its introduction more than 50 years ago, hematopoietic stem-cell transplantation (HSCT) has transformed from an inescapably fatal procedure to one where cure from malignant and other nonmalignant hematologic diseases is becoming increasingly common. Nevertheless, longevity is not entirely restored. New causes of mortality have emerged; of particular importance is that of increased cardiovascular disease (CVD), related to metabolic syndrome and its components. Controversy exists over whether the metabolic abnormalities induced are a direct effect of HSCT itself or a consequence of other therapies involved. Analysis of the mechanisms that promote the changes in metabolic components will give insight into future HSCT therapy as well as CVD pathogenesis and prevention.

Insulin Resistance as a Link between Amyloid-Beta and Tau Pathologies in Alzheimer's Disease

Current hypotheses and theories regarding the pathogenesis of Alzheimer’s disease (AD) heavily implicate brain insulin resistance (IR) as a key factor. Despite the many well-validated metrics for systemic IR, the absence of biomarkers for brain-specific IR represents a translational gap that has hindered its study in living humans. In our lab, we have been working to develop biomarkers that reflect the common mechanisms of brain IR and AD that may be used to follow their engagement by experimental treatments. We present two promising biomarkers for brain IR in AD: insulin cascade mediators probed in extracellular vesicles (EVs) enriched for neuronal origin, and two-dimensional magnetic resonance spectroscopy (MRS) measures of brain glucose. As further evidence for a fundamental link between brain IR and AD, we provide a novel analysis demonstrating the close spatial correlation between brain expression of genes implicated in IR (using Allen Human Brain Atlas data) and tau and beta-amyloid pathologies. We proceed to propose the bold hypotheses that baseline differences in the metabolic reliance on glycolysis, and the expression of glucose transporters (GLUT) and insulin signaling genes determine the vulnerability of different brain regions to Tau and/or Amyloid beta (Aβ) pathology, and that IR is a critical link between these two pathologies that define AD. Lastly, we provide an overview of ongoing clinical trials that target IR as an angle to treat AD, and suggest how biomarkers may be used to evaluate treatment efficacy and target engagement.

Parallel comparison of risk factors between progression of organic stenosis in the coronary arteries and onset of acute coronary syndrome by covariance structure analysis

Background

It is widely accepted that progression of organic stenosis in the coronary arteries and onset of acute coronary syndrome (ACS) are similar in the development of atherosclerosis. However, the extent of the association of each risk factor with the respective pathological conditions has not been fully elucidated.

Objectives

We investigated the differences in risk factors between these conditions using a statistical procedure.

Methods

The study population consisted of 1,029 patients with ischemic heart disease (IHD). We divided the study population into two groups (ACS and non-ACS) and by diseased vessels (organic stenosis). Covariance structure analysis was simultaneously performed in one equation model for determination and comparison of the risk factors for organic stenosis and ACS.

Results

The analysis revealed that age (standardized regression coefficient, β: 0.206, P < 0.001), male gender (β: 0.126, P < 0.001), HbA1c level (β: 0.109, P < 0.001), HDL level (β: -0.109, P < 0.001) and LDL level (β: 0.127, P = 0.002) were significant for the advancement of organic stenosis. HDL level (β: 0100, P = 0.002) and MDA-LDL level (β: 0.335, P < 0.001) were significant for the onset of ACS, but age, HbA1c and LDL (P = NS or β < 0.1, respectively) were not. Among the risk factors, age, HbA1c and LDL were significantly more strongly associated with organic stenosis than ACS, while MDA-LDL was significantly more strongly associated with ACS than organic stenosis.

Conclusions

The current statistical analysis revealed clear differences among the risk factors between the progression of organic stenosis and the onset of ACS. Among them, the MDA-LDL level should be considered to indicate a substantial risk of ACS.

Plasma from pre-pubertal obese children impairs insulin stimulated Nitric Oxide (NO) bioavailability in endothelial cells: Role of ER stress

Childhood obesity is commonly associated with early signs of endothelial dysfunction, characterized by impairment of insulin signaling and vascular Nitric Oxide (NO) availability. However, the underlying mechanisms remain to be established. Hence, we tested the hypothesis that endothelial insulin-stimulated NO production and availability was impaired and related to Endoplasmic Reticulum (ER) in human umbilical vein endothelial cells (HUVECs) cultured with plasma obtained from pre-pubertal obese (OB) children. OB children (N = 28, age: 8.8 ± 2.2; BMI z-score: 2.15 ± 0.39) showed impaired fasting glucose, insulin and HOMA-IR than normal weight children (CTRL; N = 28, age: 8.8 ± 1.7; BMI z-score: 0.17 ± 0.96). The in vitro experiments showed that OB-plasma significantly impaired endothelial insulin-stimulated NO production and bioavailability compared to CTRL-plasma. In parallel, in HUVECs OB-plasma increased GRP78 and activated PERK, eIF2α, IkBα and ATF6 (all ER stress markers). Moreover, OB-plasma increased NF-κB activation and its nuclear translocation. Notably, all these effects proved to be significantly restored by using PBA and TUDCA, known ER stress inhibitors. Our study demonstrate for the first time that plasma from obese children is able to induce in vitro endothelial insulin resistance, which is characterized by reduced insulin-stimulated NO production and bioavailability, endothelial ER stress and increased NF-κB activation.

Levels of metabolic markers in drug-naive prediabetic and type 2 diabetic patients

AIMS

Type 2 diabetes mellitus (T2DM) and prediabetes (pre-DM) are associated with changes in levels of metabolic markers. The main aim of this study is to compare the levels of omentin, irisin, endothelin-1, nesfatin, hepatocyte growth factor (HGF), fibroblast growth factor, and oxytocin (OXT) between normoglycemic and pre-DM/T2DM obese Jordanian patients.

METHODS

One hundred and ninety-eight adult Jordanian subjects were recruited. Demographic data and clinical parameters were collected. The serum levels of biomarkers were measured by enzymatic assay procedure.

RESULTS

Compared to normoglycemic (95 subjects), pre-DM/T2DM (103 subjects) displayed higher HGF (ng/ml) = 78.8 (71.4-104) versus 55.9 (45.3-66.6), p < 0.0001; and nesfatin (ng/ml) = 0.5 (0.4-0.7) versus 0.2 (0.1-0.4), p < 0.0001; betatrophin (ng/ml) = 1.2 (0.8-1.6) versus 0.22 (0.15-0.41), p < 0.0001. On the other hand, they had lower levels of omentin (ng/ml) = 2.1 (0.9-3.3) versus 3.6 (2.0-6.4), p < 0.0001, irisin (ng/ml) = 113.7 (88.9-142.9) versus 132.6 (110.7-147.8), p < 0.0001; and oxytocin (pg/ml) = 1077.9 (667.3-1506.0) versus 2180.1 (1464.5-2795.6), p < 0.0001; respectively. In comparison, FGF-21 (ng/ml) = 0.3 (0.2-0.5) versus 0.2 (0.1-0.4), and endothelin (pg/ml) = 2.7 (1.3-5.2) versus 2.8 (1.6-5.6) did not differ between the two groups (p > 0.05).

CONCLUSIONS

In the present study, patients with pre-DM and T2DM have higher serum levels of metabolic HGF, nesfatin, and betatrophin and lower levels of omentin, irisin, and OXT. Future longitudinal and interventional studies are required to confirm the utility of these markers as novel progression or therapeutic targets in the pharmacotherapy of diabetes.

Akt/mTOR Role in Human Foetoplacental Vascular Insulin Resistance in Diseases of Pregnancy

Insulin resistance is characteristic of pregnancies where the mother shows metabolic alterations, such as preeclampsia (PE) and gestational diabetes mellitus (GDM), or abnormal maternal conditions such as pregestational maternal obesity (PGMO). Insulin signalling includes activation of insulin receptor substrates 1 and 2 (IRS1/2) as well as Src homology 2 domain-containing transforming protein 1, leading to activation of 44 and 42 kDa mitogen-activated protein kinases and protein kinase B/Akt (Akt) signalling cascades in the human foetoplacental vasculature. PE, GDM, and PGMO are abnormal conditions coursing with reduced insulin signalling, but the possibility of the involvement of similar cell signalling mechanisms is not addressed. This review aimed to determine whether reduced insulin signalling in PE, GDM, and PGMO shares a common mechanism in the human foetoplacental vasculature. Insulin resistance in these pathological conditions results from reduced Akt activation mainly due to inhibition of IRS1/2, likely due to the increased activity of the mammalian target of rapamycin (mTOR) resulting from lower activity of adenosine monophosphate kinase. Thus, a defective signalling via Akt/mTOR in response to insulin is a central and common mechanism of insulin resistance in these diseases of pregnancy. In this review, we summarise the cell signalling mechanisms behind the insulin resistance state in PE, GDM, and PGMO focused in the Akt/mTOR signalling pathway in the human foetoplacental endothelium.

Role of endoplasmic reticulum stress signalling in diabetic endothelial dysfunction and atherosclerosis

It is well established that diabetes mellitus accelerates atherosclerotic vascular disease. Endothelial injury has been proposed to be the initial event in the pathogenesis of atherosclerosis. Endothelium not only acts as a semi-selective barrier but also serves physiological and metabolic functions. Diabetes or high glucose in circulation triggers a series of intracellular responses and organ damage such as endothelial dysfunction and apoptosis. One such response is high glucose-induced chronic endoplasmic reticulum stress in the endothelium. The unfolded protein response is an acute reaction that enables cells to overcome endoplasmic reticulum stress. However, when chronically persistent, endoplasmic reticulum stress response could ultimately lead to endothelial dysfunction and atherosclerosis. Herein, we discuss the scientific advances in understanding endoplasmic reticulum stress-induced endothelial dysfunction, the pathogenesis of diabetes-accelerated atherosclerosis and endoplasmic reticulum stress as a potential target in therapies for diabetic atherosclerosis.

Cyanidin-3-O-glucoside ameliorates palmitate-induced insulin resistance by modulating IRS-1 phosphorylation and release of endothelial derived vasoactive factors

Increased plasma levels of free fatty acids, including palmitic acid (PA), cause insulin resistance in endothelium characterized by a decreased synthesis of insulin-mediated vasodilator nitric oxide (NO), and by an increased production of the vasoconstrictor protein, endothelin-1. Several in vitro and in vivo studies suggest that anthocyanins, natural phenols commonly present in food and vegetables from Mediterranean Diet, exert significant cardiovascular health-promoting activities. These effects are possibly mediated by a positive regulation of the transcription factor Nrf2 and activation of cellular antioxidant and cytoprotective genes. The present study examined, at a molecular level, the effects of cyanidin-3-O-glucoside (C3G), a widely distributed anthocyanin, on PA-induced endothelial dysfunction and insulin resistance in human umbilical vein endothelial cells (HUVECs). Our results indicate that C3G pretreatment effectively reverses the effects of PA on PI3K/Akt axis, and restores eNOS expression and NO release, altered by PA. We observed that these effects were exerted by changes on the phosphorylation of IRS-1 on specific serine and tyrosine residues modulated by PA through the modulation of JNK and IKK activity. Furthermore, silencing Nrf2 transcripts demonstrated that the protective effects of C3G are directly related to the activation of Nrf2.

Association of peripheral nesfatin-1 with early stage diabetic nephropathy

BACKGROUND

Nesfatin-1 is a newly found anorectic neuropeptide with potent metabolic regulatory effects that its circulating levels are shown to be elevated in diabetes. We compared serum nesfatin-1 in patients with type 2 diabetes and microalbuminuria (30mg/day≤urinary albumin excretion (UAE) <300mg/day) with their control patients with type 2 diabetes and normoalbuminuria (UAE <30mg/day).

PATIENTS AND METHODS

In a cross sectional setting, 44 adult patients with type 2 diabetes and microalbuminuria and 44 control patients with type 2 diabetes and normoalbuminuria were evaluated. Serum levels of nesfatin-1 along with demographic, clinical and biochemical factors associated with diabetes was measured.

RESULTS

Mean peripheral concentrations of nesfatin-1 were significantly higher in patients with diabetes who had microalbuminuria compared to normoalbuminuric control patients (175.27±25.96pg/ml vs. 134.66±23.18pg/ml, respectively; p value<0.001). Significant positive correlations were found between circulating nesfatin-1 levels and the following case-mix variables: duration of diabetes, glycated hemoglobin, plasma creatinine, UAE and serum uric acid. In the multivariate logistic regression and after adjustment for a constellation of potentially confounding variables associated with diabetic kidney disease (DKD), circulating nesfatin-1 was the only variable significantly associated with microalbuminuria (odds ratio [95% confidence interval]=1.224 [1.007-1.487], p value=0.042).

CONCLUSION

In patients with type 2 diabetes, circulating nesfatin-1 appears to be associated with microalbuminuria independent of other established risk factors of DKD. The underlying pathophysiological mechanisms and the prognostic significance of this association remain to be elucidated.

Type of supplemented simple sugar, not merely calorie intake, determines adverse effects on metabolism and aortic function in female rats

High consumption of simple sugars causes adverse cardiometabolic effects. We investigated the mechanisms underlying the metabolic and vascular effects of glucose or fructose intake and determined whether these effects are exclusively related to increased calorie consumption. Female Sprague-Dawley rats were supplemented with 20% wt/vol glucose or fructose for 2 mo, and plasma analytes and aortic response to vasodilator and vasoconstrictor agents were determined. Expression of molecules associated with lipid metabolism, insulin signaling, and vascular response were evaluated in hepatic and/or aortic tissues. Caloric intake was increased in both sugar-supplemented groups vs. control and in glucose- vs. fructose-supplemented rats. Hepatic lipogenesis was induced in both groups. Plasma triglycerides were increased only in the fructose group, together with decreased expression of carnitine palmitoyltransferase-1A and increased microsomal triglyceride transfer protein expression in the liver. Plasma adiponectin and peroxisome proliferator-activated receptor (PPAR)-α expression was increased only by glucose supplementation. Insulin signaling in liver and aorta was impaired in both sugar-supplemented groups, but the effect was more pronounced in the fructose group. Fructose supplementation attenuated aortic relaxation response to a nitric oxide (NO) donor, whereas glucose potentiated it. Phenylephrine-induced maximal contractions were reduced in the glucose group, which could be related to increased endothelial NO synthase (eNOS) phosphorylation and subsequent elevated basal NO in the glucose group. In conclusion, despite higher caloric intake in glucose-supplemented rats, fructose caused worse metabolic and vascular responses. This may be because of the elevated adiponectin level and the subsequent enhancement of PPARα and eNOS phosphorylation in glucose-supplemented rats.

NEW & NOTEWORTHY

This is the first study comparing the effects of glucose and fructose consumption on metabolic factors and aortic function in female rats. Our results show that, although total caloric consumption was higher in glucose-supplemented rats, fructose ingestion had a greater impact in inducing metabolic and aortic dysfunction.

Insulin Downregulates the Transcriptional Coregulator CITED2, an Inhibitor of Proangiogenic Function in Endothelial Cells

In patients with atherosclerotic complications of diabetes, impaired neovascularization of ischemic tissue in the myocardium and lower limb limits the ability of these tissues to compensate for poor perfusion. We identified 10 novel insulin-regulated genes, among them Adm, Cited2, and Ctgf, which were downregulated in endothelial cells by insulin through FoxO1. CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2), which was downregulated by insulin by up to 54%, is an important negative regulator of hypoxia-inducible factor (HIF) and impaired HIF signaling is a key mechanism underlying the impairment of angiogenesis in diabetes. Consistent with impairment of vascular insulin action, CITED2 was increased in cardiac endothelial cells from mice with diet-induced obesity and from db/db mice and was 3.8-fold higher in arterial tissue from patients with type 2 diabetes than control subjects without diabetes. CITED2 knockdown promoted endothelial tube formation and endothelial cell proliferation, whereas CITED2 overexpression impaired HIF activity in vitro. After femoral artery ligation, induction of an endothelial-specific HIF target gene in hind limb muscle was markedly upregulated in mice with endothelial cell deletion of CITED2, suggesting that CITED2 can limit HIF activity in vivo. We conclude that vascular insulin resistance in type 2 diabetes contributes to the upregulation of CITED2, which impairs HIF signaling and endothelial proangiogenic function.

HMGA1 is a novel candidate gene for myocardial infarction susceptibility

BACKGROUND

Acute Myocardial infarction (AMI), a leading cause of morbidity and mortality worldwide, is a dreadful acute complication of coronary atherosclerosis. Type 2 diabetes mellitus (T2DM) is associated with an increased risk of developing AMI. The architectural transcription factor high-mobility-group AT-hook 1 (HMGA1) has been involved in atherosclerosis, plaque formation, inflammation, and in the pathogenesis of insulin resistance and T2DM. An association of the HMGA1 rs146052672 variant with T2DM has been recently reported. Thus, our aim was to evaluate whether this variant was also associated with AMI.

METHODS AND RESULTS

In a case-control study from Calabria (Southern Italy), we enrolled 254 consecutive, unrelated, patients with first diagnosis of AMI, and 508 age, sex-matched controls. Genotyping of the rs146052672 was performed using the TaqMan allelic discrimination method. We found that this variant was present in 7.9% of AMI patients and in 3.1% of controls (p=0.003). Multiple logistic regression confirmed that the rs146052672 was significantly associated with AMI (OR=2.54; p=0.002), and this association was independent of classical cardiovascular risk factors such as gender, hypertension, obesity and T2DM (for all, p<0.05).

CONCLUSIONS

Our findings demonstrate that a relationship exists between the HMGA1 rs146052672 variant and AMI, suggesting that defects at the HMGA1 locus may play a pathogenetic role in AMI, in the absence of T2DM and other cardiovascular risk factors.

Selective association of electrocardiographic abnormalities with insulin sensitivity and beta-cell function in type 2 diabetes mellitus: a cross-sectional analysis

BACKGROUND

We investigated the association of electrocardiographic (ECG) abnormalities with markers of insulin resistance and pancreatic beta-cell dysfunction in a cross-sectional study of type 2 diabetes patients.

METHODS

Electrocardiographic criteria were evaluated in the Penn Diabetes Heart Study participants (n = 1671; 64% male; 61% Caucasian), including a sub-sample (n = 710) that underwent oral glucose tolerance testing. The Matsuda Insulin Sensitivity Index and homeostasis model assessment of insulin resistance (HOMA-IR) estimated insulin sensitivity; Insulinogenic Index and homeostasis model assessment of beta-cell function assessed beta-cell function. Multivariable regression modelling was used to analyse associations of ECG changes with these indices.

RESULTS

In unadjusted analyses, subjects in the highest quartile of Matsuda index had the lowest prevalence of Q-waves (6.3% versus 15.3%, p = 0.005). In adjusted models, an inverse association was seen between Q-waves and log Matsuda index [one standard deviation increase; OR = 0.59 (95% CI 0.43-0.87 p = 0.001)]. In the full Penn Diabetes Heart Study, there was a direct association between Q-waves and HOMA-IR [one standard deviation increase; OR = 1.43 (95% CI 1.13-1.81, p = 0.003)]. In adjusted models, left ventricular hypertrophy also was inversely associated with Matsuda index and directly with HOMA-IR. Higher Insulinogenic Index scores were associated with a lower prevalence of nonspecific ST changes [OR = 0.78 (95% CI 0.62-0.98, p = 0.032)].

CONCLUSIONS

In type 2 diabetic patients, both oral glucose tolerance testing-derived and HOMA-derived measures of insulin resistance were associated with pathologic Q-waves and left ventricular hypertrophy on ECGs. Copyright © 2016 John Wiley & Sons, Ltd.

TNF-α induces vascular insulin resistance via positive modulation of PTEN and decreased Akt/eNOS/NO signaling in high fat diet-fed mice

BACKGROUND

High fat diet (HFD) induces insulin resistance in various tissues, including the vasculature. HFD also increases plasma levels of TNF-α, a cytokine that contributes to insulin resistance and vascular dysfunction. Considering that the enzyme phosphatase and tension homologue (PTEN), whose expression is increased by TNF-α, reduces Akt signaling and, consequently, nitric oxide (NO) production, we hypothesized that PTEN contributes to TNF-α-mediated vascular resistance to insulin induced by HFD. Mechanisms underlying PTEN effects were determined.

METHODS

Mesenteric vascular beds were isolated from C57Bl/6J and TNF-α KO mice submitted to control or HFD diet for 18 weeks to assess molecular mechanisms by which TNF-α and PTEN contribute to vascular dysfunction.

RESULTS

Vasodilation in response to insulin was decreased in HFD-fed mice and in ex vivo control arteries incubated with TNF-α. TNF-α receptors deficiency and TNF-α blockade with infliximab abolished the effects of HFD and TNF-α on insulin-induced vasodilation. PTEN vascular expression (total and phosphorylated isoforms) was increased in HFD-fed mice. Treatment with a PTEN inhibitor improved insulin-induced vasodilation in HFD-fed mice. TNF-α receptor deletion restored PTEN expression/activity and Akt/eNOS/NO signaling in HFD-fed mice.

CONCLUSION

TNF-α induces vascular insulin resistance by mechanisms that involve positive modulation of PTEN and inhibition of Akt/eNOS/NO signaling. Our findings highlight TNF-α and PTEN as potential targets to limit insulin resistance and vascular complications associated with obesity-related conditions.

Role of habitual physical activity in modulating vascular actions of insulin

NEW FINDINGS

What is the topic of this review? This review highlights the importance of increased vascular insulin sensitivity for maintaining glycaemic control and cardiovascular health. What advances does it highlight? We discuss the role of habitual physical activity in modulating vascular actions of insulin. Type 2 diabetes and cardiovascular disease commonly coexist. Current evidence suggests that impaired insulin signalling in the vasculature may be a common link between metabolic and cardiovascular diseases, including glycaemic dysregulation and atherosclerosis. Herein, we highlight the importance of the actions of insulin on the vasculature for glycaemic control and arterial health. In addition, we summarize and discuss findings from our group and others demonstrating that increased physical activity may be an effective approach to enhancing vascular insulin sensitivity. Furthermore, in light of the existing literature, we formulate the hypothesis that increased shear stress may be a prime mechanism through which habitual physical activity improves insulin signalling in the vasculature. Ultimately, we propose that targeting vascular insulin resistance may represent a viable strategy for improving glycaemic control and reducing cardiovascular risk in patients with type 2 diabetes.

Treatment of insulin resistance by acupuncture: a review of human and animal studies

BACKGROUND

Numerous experimental studies have demonstrated that acupuncture can correct various metabolic disorders such as hyperglycaemia, overweight, hyperphagia, hyperlipidaemia, inflammation, altered activity of the sympathetic nervous system, and insulin signalling defects, all of which contribute to the development of insulin resistance.

OBJECTIVE

To review human and animal studies investigating acupuncture as a treatment for insulin resistance, and to evaluate its potential to increase insulin sensitivity.

METHODS

PubMed was searched for relevant articles published between January 2008 and October 2015. Search terms used were 'acupuncture', 'insulin resistance', 'insulin sensitivity', and 'blood glucose'. Additional secondary sources of information included reference lists from retrieved papers and pertinent papers identified by hand searches of relevant journals not found in the database.

RESULTS

In total, 31 articles were included in this review and comprised studies of the following insulin resistant conditions: obesity (n=9); diabetes mellitus (n=12); polycystic ovarian syndrome (n=7); skeletal muscle atrophy (n=1); ischaemic heart disease (n=1); and fatty liver disease (n=1). Of these articles, seven were human trials and 24 animal experiments. Collectively, the studies suggest that electroacupuncture (EA) at low intensity and low frequency can reduce insulin resistance and increase insulin sensitivity in a range of different insulin-resistant conditions.

CONCLUSIONS

EA, used alone or in combination with other therapies, such as Chinese herbs or diet-exercise interventions, has the potential to be an effective treatment for insulin resistance. Additional controlled clinical studies of acupuncture are needed in subjects with diabetes mellitus, ischaemic heart disease, muscle atrophy, and fatty liver disease.

Epicardial Fat: Physiological, Pathological, and Therapeutic Implications

Epicardial fat is closely related to blood supply vessels, both anatomically and functionally, which is why any change in this adipose tissue's behavior is considered a potential risk factor for cardiovascular disease development. When proinflammatory adipokines are released from the epicardial fat, this can lead to a decrease in insulin sensitivity, low adiponectin production, and an increased proliferation of vascular smooth muscle cells. These adipokines move from one compartment to another by either transcellular passing or diffusion, thus having the ability to regulate cardiac muscle activity, a phenomenon called vasocrine regulation. The participation of these adipokines generates a state of persistent vasoconstriction, increased stiffness, and weakening of the coronary wall, consequently contributing to the formation of atherosclerotic plaques. Therefore, epicardial adipose tissue thickening should be considered a risk factor in the development of cardiovascular disease, a potential therapeutic target for cardiovascular pathology and a molecular point of contact for "endocrine-cardiology."

Additive Effect of Non-Alcoholic Fatty Liver Disease on Metabolic Syndrome-Related Endothelial Dysfunction in Hypertensive Patients

Metabolic syndrome (MS) is characterized by an increased risk of incident diabetes and cardiovascular (CV) events, identifying insulin resistance (IR) and endothelial dysfunction as key elements. Moreover, non-alcoholic fatty liver disease (NAFLD) is bidirectionally linked with MS as a consequence of metabolic and inflammatory abnormalities. We addressed the question if the evolution in NAFLD might worsen endothelium-dependent vasodilating response in MS hypertensives. We recruited 272 Caucasian newly-diagnosed never-treated hypertensive outpatients divided into three groups according to the presence/absence of MS alone or in combination with NAFLD. MS and NAFLD were defined according to the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII) and non-invasive fatty liver index, respectively. We determined IR by using the homeostasis model assessment (HOMA) index. Vascular function, as forearm blood flow (FBF), was determined through strain-gauge plethysmography after intra-arterial infusion of acetylcholine (ACh) and sodium nitroprusside. MS+NAFLD+ group showed worse metabolic, inflammatory and vascular profiles compared with MS−NAFLD− and MS+NAFLD−. HOMA resulted in being the strongest predictor of FBF both in the MS+NAFLD− and in the MS+NAFLD+ groups, accounting for 20.5% and 33.2% of its variation, respectively. In conclusion, we demonstrated that MS+NAFLD+ hypertensives show a worse endothelium-dependent vasodilation compared with MS+NAFLD−, allowing for consideration of NAFLD as an early marker of endothelial dysfunction in hypertensives.

Dietary Fructose Activates Insulin Signaling and Inflammation in Adipose Tissue: Modulatory Role of Resveratrol

The effects of high-fructose diet on adipose tissue insulin signaling and inflammatory process have been poorly documented. In this study, we examined the influences of long-term fructose intake and resveratrol supplementation on the expression of genes involved in insulin signaling and the levels of inflammatory cytokines and sex hormones in the white adipose tissues of male and female rats. Consumption of high-fructose diet for 24 weeks increased the expression of genes involved in insulin signaling including IR, IRS-1, IRS-2, Akt, PI3K, eNOS, mTOR, and PPARγ, despite induction of proinflammatory markers, iNOS, TNFα, IL-1β, IL-18, MDA, and ALT, as well as anti-inflammatory factors, IL-10 and Nrf2 in adipose tissues from males and females. Total and free testosterone concentrations of adipose tissues were impaired in males but increased in females, although there were no changes in their blood levels. Resveratrol supplementation markedly restored the levels of MDA, IL6, IL-10, and IL-18, as well as iNOS, Nrf2, and PI3K mRNA, in adipose tissues of both genders. Dietary fructose activates both insulin signaling and inflammatory pathway in the adipose tissues of male and female rats proposing no correlation between the tissue insulin signaling and inflammation. Resveratrol has partly modulatory effects on fructose-induced changes.

MicroRNA-181b Improves Glucose Homeostasis and Insulin Sensitivity by Regulating Endothelial Function in White Adipose Tissue

RATIONALE

The pathogenesis of insulin resistance involves dysregulated gene expression and function in multiple cell types, including endothelial cells (ECs). Post-transcriptional mechanisms such as microRNA-mediated regulation of gene expression could affect insulin action by modulating EC function.

OBJECTIVE

To determine whether microRNA-181b (miR-181b) affects the pathogenesis of insulin resistance by regulating EC function in white adipose tissue during obesity.

METHODS AND RESULTS

MiR-181b expression was reduced in adipose tissue ECs of obese mice, and rescue of miR-181b expression improved glucose homeostasis and insulin sensitivity. Systemic intravenous delivery of miR-181b robustly accumulated in adipose tissue ECs, enhanced insulin-mediated Akt phosphorylation at Ser473, and reduced endothelial dysfunction, an effect that shifted macrophage polarization toward an M2 anti-inflammatory phenotype in epididymal white adipose tissue. These effects were associated with increased endothelial nitric oxide synthase and FoxO1 phosphorylation as well as nitric oxide activity in epididymal white adipose tissue. In contrast, miR-181b did not affect insulin-stimulated Akt phosphorylation in liver and skeletal muscle. Bioinformatics and gene profiling approaches revealed that Pleckstrin homology domain leucine-rich repeat protein phosphatase, a phosphatase that dephosphorylates Akt at Ser473, is a novel target of miR-181b. Knockdown of Pleckstrin homology domain leucine-rich repeat protein phosphatase increased Akt phosphorylation at Ser473 in ECs, and phenocopied miR-181b's effects on glucose homeostasis, insulin sensitivity, and inflammation of epididymal white adipose tissue in vivo. Finally, ECs from diabetic subjects exhibited increased Pleckstrin homology domain leucine-rich repeat protein phosphatase expression.

CONCLUSIONS

Our data underscore the importance of adipose tissue EC function in controlling the development of insulin resistance. Delivery of miR-181b or Pleckstrin homology domain leucine-rich repeat protein phosphatase inhibitors may represent a new therapeutic approach to ameliorate insulin resistance by improving adipose tissue endothelial Akt-endothelial nitric oxide synthase-nitric oxide signaling.

The prothrombotic state associated with obesity-induced hypertension is reduced by cocoa and its main flavanols

Cocoa flavanols could ameliorate cardiovascular health in obese patients.

The ergogenic supplement β-hydroxy-β-methylbutyrate (HMB) attenuates insulin resistance through suppressing GLUT-2 in rat liver

This study investigates the effect of the ergogenic supplement β-hydroxy-β-methylbutyrate (HMB) on insulin resistance induced by high-fructose diet (HFD) in rats. Male Sprague Dawley rats were fed 60% HFD for 12 weeks and HMB (320 mg·kg(-1)·day(-1), orally) for 4 weeks. HFD significantly increased fasting insulin, fasting glucose, glycosylated hemoglobin (HBA1C), liver glycogen content, and homeostasis model assessment of insulin resistance (HOMA-IR) index, while it decreased glucose and insulin tolerance. Furthermore, HFD significantly increased serum triglycerides (TG), low density lipoprotein cholesterol (LDL-C), and very low density lipoprotein cholesterol (VLDL-C) levels, while it significantly decreased high density lipoprotein cholesterol (HDL-C). Moreover, HFD significantly increased mRNA expression of glucose transporter type-2 (GLUT-2), the mammalian target of rapamycin (mTOR), and sterol regulatory element-binding protein-1c (SREBP-1c) but decreased peroxisome proliferator-activated receptor-alpha (PPAR-α) in liver. Aortic relaxation to acetylcholine (ACh) was impaired and histopathology showed severe hepatic steatosis. HMB significantly increased insulin tolerance and decreased fasting insulin, HOMA-IR, HBA1C, hepatic glycogen content, serum TG, LDL-C, and VLDL-C. Additionally, HMB enhanced ACh-induced relaxation, ameliorated hepatic steatosis, and decreased mRNA expression of GLUT-2. In conclusion, HMB may attenuate insulin resistance and hepatic steatosis through inhibiting GLUT-2 in liver.