Endothelial Insulin Sensitivity Research Articles

The role of SGLT2i in attenuating residual cardiovascular risk through blood pressure-lowering: mechanistic insights and perspectives.

Sodium glucose cotransporter 2 inhibitors (SGLT2) have been increasingly pursued as a promising target for addressing residual cardiovascular risk. Prior trials demonstrated that SGLT2i not only promotes glucose-lowering, but also improves endothelial dysfunction, adiposity, fluid overload, and insulin sensitivity thus contributing to hemodynamic changes implicated in its cardiorenal benefits. The mechanisms in the effect of SGLT2i on blood pressure and their potential role in preventing cardiovascular events are hereby revised.

Endothelial HSP72 is not reduced in type 2 diabetes nor is it a key determinant of endothelial insulin sensitivity.

Impaired endothelial insulin signaling and consequent blunting of insulin-induced vasodilation is a feature of type 2 diabetes (T2D) that contributes to vascular disease and glycemic dysregulation. However, the molecular mechanisms underlying endothelial insulin resistance remain poorly known. Herein, we tested the hypothesis that endothelial insulin resistance in T2D is attributed to reduced expression of heat shock protein 72 (HSP72). HSP72 is a cytoprotective chaperone protein that can be upregulated with heating and is reported to promote insulin sensitivity in metabolically active tissues, in part via inhibition of JNK activity. Accordingly, we further hypothesized that, in individuals with T2D, 7 days of passive heat treatment via hot water immersion to waist level would improve leg blood flow responses to an oral glucose load (i.e., endogenous insulin stimulation) via induction of endothelial HSP72. In contrast, we found that: 1) endothelial insulin resistance in T2D mice and humans was not associated with reduced HSP72 in aortas and venous endothelial cells, respectively; 2) after passive heat treatment, improved leg blood flow responses to an oral glucose load did not parallel with increased endothelial HSP72; and 3) downregulation of HSP72 (via small-interfering RNA) or upregulation of HSP72 (via heating) in cultured endothelial cells did not impair or enhance insulin signaling, respectively, nor was JNK activity altered. Collectively, these findings do not support the hypothesis that reduced HSP72 is a key driver of endothelial insulin resistance in T2D but provide novel evidence that lower-body heating may be an effective strategy for improving leg blood flow responses to glucose ingestion-induced hyperinsulinemia.

Role of Polyphenols and Carotenoids in Endothelial Dysfunction: An Overview from Classic to Innovative Biomarkers.

Nowadays, the dramatically increased prevalence of metabolic diseases, such as obesity and diabetes mellitus and their related complications, including endothelial dysfunction and cardiovascular disease, represents one of the leading causes of death worldwide. Dietary nutrients together with healthy lifestyles have a crucial role in the endothelium health-promoting effects. From a growing body of evidence, active natural compounds from food, including polyphenols and carotenoids, have attracted particular attention as a complementary therapy on atherosclerosis and cardiovascular disease, as well as preventive approaches through the attenuation of inflammation and oxidative stress. They mainly act as radical scavengers by promoting a variety of biological mechanisms, such as improvements in endothelial function, blood pressure, platelet activity, and insulin sensitivity, and by modulating various known biomarkers. The present review highlights the role of polyphenols and carotenoids in early endothelial dysfunction with attention to their beneficial effect in modulating both classical and recent technologically generated emerging biomarkers. These, alone or in combination, can play an important role in the prediction, diagnosis, and evolution of cardiovascular disease. However, a main challenge is to speed up early and prompt new interventions in order to prevent or slow down disease progression, even with an adequate intake of bioactive compounds. Hence, there is an urgent need of new more validated, appropriate, and reliable diagnostic and therapeutic biomarkers useful to diagnose endothelial dysfunction at an earlier stage.

Quercetin improves endothelial insulin sensitivity in obese mice by inhibiting Drp1 phosphorylation at serine 616 and mitochondrial fragmentation.

Studies have shown that endothelial insulin resistance induced by oxidative stress contributes to vascular dysfunction in metabolic disorders. Quercetin, a natural antioxidant, has been recently shown to exert protective effects on endothelial function. However, the effects of quercetin on endothelial insulin resistance and its underlying mechanism are unclear. Here, we found that chronic oral treatment of obese mice with quercetin increased vascular endothelial insulin sensitivity, accompanied by alleviated mitochondrial fragmentation as revealed by confocal imaging. In addition, western blot analysis showed that quercetin treatment suppressed the levels of dynamin-related protein 1 (Drp1) and phosphorylation at serine 616 in endothelial cells of obese mice. Mechanistically, quercetin specifically suppressed Drp1 phosphorylation at serine 616, whereas it showed little effects on the Drp1 level and its phosphorylation at serine 637 in cultured endothelial cells under oxidative stress. Furthermore, our results also showed that quercetin suppressed Drp1 phosphorylation at serine 616 by inhibiting PKCδ as revealed by western blot analysis. Knockdown of PKCδ with siRNA alleviated the protective effects of quercetin on endothelial-mitochondrial dynamics and insulin sensitivity. These results suggest that chronic oral treatment with quercetin exerts endothelial protective effects through inhibition of PKCδ and the resultant mitochondrial fragmentation.

Reducing sitting time versus adding exercise: differential effects on biomarkers of endothelial dysfunction and metabolic risk

Recent studies suggest that substituting sitting with light physical activity has beneficial metabolic effects, but it is unclear if this is associated with parallel changes in endothelial function. Data from three randomized cross-over studies were analyzed, in which 61 subjects (with normal weight, overweight and type 2 diabetes) followed different activity regimens (Sit, SitLess and/or Exercise) of four days each. Subjects were instructed to sit 14 h/day (‘Sit’), to substitute 1 h/day of sitting with moderate-to-vigorous cycling (‘Exercise’) or to substitute 5–6 h/day sitting with light-intensity walking and standing (‘SitLess’). Physical activity was assessed 24 h/day by accelerometry (ActivPAL) and diet was standardized. Fasted circulating biomarkers of endothelial dysfunction, lipids and insulin sensitivity were assessed the morning after each activity regimen. The endothelial dysfunction score (ED-score) was computed by averaging the Z-scores of the circulating biomarkers of endothelial dysfunction. Compared to Sit, Exercise resulted in lower ED-score, sICAM1 and sE-selectin (p < 0.05), while no significant changes were observed after SitLess. The ED-score, sVCAM1 and sE-selectin were lower after Exercise compared to SitLess (p < 0.05). In contrast, compared to Sit, insulin sensitivity (HOMA2-IR) and plasma lipids (HDL-cholesterol, non-HDL-cholesterol, total cholesterol and Apo B) did not change significantly after Exercise but were improved after SitLess (p < 0.05). In conclusion, light physical activity and moderate-to-vigorous physical activity had a differential effect on risk markers of cardio-metabolic health and suggest the need of both performing structured exercise as well as reducing sitting time on a daily basis.

ATP2B1 gene Silencing Increases Insulin Sensitivity through Facilitating Akt Activation via the Ca2+/calmodulin Signaling Pathway and Ca2+-associated eNOS Activation in Endothelial Cells.

Endothelial cell insulin resistance may be partially responsible for the higher risk of atherosclerosis and cardiovascular disease in populations with insulin resistance and type 2 diabetes mellitus (T2DM). A genome-wide association study revealed a significant association between the ATPase plasma membrane Ca2+ transporting 1 (ATP2B1) gene and T2DM in two community-based cohorts from the Korea Association Resource Project. However, little is known about the implication of the ATP2B1 gene on T2DM. In the present study, we investigated the role of the ATP2B1 gene in endothelial cell insulin sensitivity. ATP2B1 gene silencing resulted in enhanced intracellular calcium concentrations and increased insulin-induced Akt activation compared to that in the negative siRNA-transfected HUVECs (Human Umbilical Vein Endothelial Cells). The elevated insulin sensitivity mediated by ATP2B1 gene silencing was Ca2+/calmodulin-dependent, as verified by administration of the calcium chelator BAPTA-AM or the calmodulin-specific antagonist W7. Moreover, higher levels of phosphorylation of eNOS (Ser1177) were observed in ATP2B1-silenced HUVECs. In addition to BAPTA-AM and W7, L-NAME, an eNOS antagonist, abolished insulin-induced Akt phosphorylation at Ser473 in both si-Neg and si-ATP2B1-transfected endothelial cells. These results indicate that the enhanced insulin sensitivity in ATP2B1-silenced endothelial cells is alternatively dependent on an increase in intracellular Ca2+ and the subsequent activation of the Ca2+/calmodulin/eNOS/Akt signaling pathway. In summary, ATP2B1 gene silencing increased insulin sensitivity in endothelial cells by directly modulating the Ca2+/calmodulin signaling pathway and via the Ca2+/calmodulin/eNOS/Akt signaling pathway alternatively.

Selective Enhancement of Insulin Sensitivity in the Endothelium In Vivo Reveals a Novel Proatherosclerotic Signaling Loop.

In the endothelium, insulin stimulates endothelial NO synthase (eNOS) to generate the antiatherosclerotic signaling radical NO. Insulin-resistant type 2 diabetes mellitus is associated with reduced NO availability and accelerated atherosclerosis. The effect of enhancing endothelial insulin sensitivity on NO availability is unclear. To answer this question, we generated a mouse with endothelial cell (EC)-specific overexpression of the human insulin receptor (hIRECO) using the Tie2 promoter-enhancer. hIRECO demonstrated significant endothelial dysfunction measured by blunted endothelium-dependent vasorelaxation to acetylcholine, which was normalized by a specific Nox2 NADPH oxidase inhibitor. Insulin-stimulated phosphorylation of protein kinase B was increased in hIRECO EC as was Nox2 NADPH oxidase-dependent generation of superoxide, whereas insulin-stimulated and shear stress-stimulated eNOS activations were blunted. Phosphorylation at the inhibitory residue Y657 of eNOS and expression of proline-rich tyrosine kinase 2 that phosphorylates this residue were significantly higher in hIRECO EC. Inhibition of proline-rich tyrosine kinase 2 improved insulin-induced and shear stress-induced eNOS activation in hIRECO EC. Enhancing insulin sensitivity specifically in EC leads to a paradoxical decline in endothelial function, mediated by increased tyrosine phosphorylation of eNOS and excess Nox2-derived superoxide. Increased EC insulin sensitivity leads to a proatherosclerotic imbalance between NO and superoxide. Inhibition of proline-rich tyrosine kinase 2 restores insulin-induced and shear stress-induced NO production. This study demonstrates for the first time that increased endothelial insulin sensitivity leads to a proatherosclerotic imbalance between NO and superoxide.

Obesity, endothelial function and inflammation: the effects of weight loss after bariatric surgery.

Obesity is associated with a high risk for atherosclerotic cardiovascular disease. There is a causal association between obesity, inflammation, insulin resistance (IR) and endothelial dysfunction. The aim of this study was to evaluate changes in IR, proinflammatory state and markers of endothelial dysfunction in morbidly obese patients after weight loss following bariatric surgery. In this study, we measured the levels of soluble intracellular adhesion molecule-1 (sICAM1), plasminogen activator inhibitor 1 (PAI-1), high-sensitivity C-reactive protein (hs-CRP), and interleukin-6 (IL-6) in 79 morbidly obese patients at baseline and 3, 6 and 12 months after gastric bypass. Also, we evaluated changes in IR. Twelve months after surgery, there was a significant decrease in plasma levels of sICAM1 (p < 0.001), PAI-1 (p < 0.05), hs-CRP (p < 0.001), IL-6 (p < 0.001) and homeostasis model assessment (HOMA) (p < 0.001) and a significant increase of McAuley index (McAuley) (p < 0.001). Baseline levels of hs-PCR were positively correlated with sICAM-1 (r = 0.450, p < 0.01) and IL-6 (r = 0.451, p < 0.01). Significant correlations were also found between the decrease of PAI-1 and the decrease of hs-PCR (r = 0.425, p < 0.01) and tryglicerides (r = 0.351, p < 0.01). In patients with morbid obesity, substantial surgically induced weight loss is followed by a significant improvement in the endothelial function, inflammatory state and insulin sensitivity, that may reduce their cardiovascular risk. A relationship exists between improved inflammatory profile and endothelial function.

The role of miR-190a in methylglyoxal-induced insulin resistance in endothelial cells

Methylglyoxal (MGO) is a reactive dicarbonyl produced as by-product of glycolysis, and its formation is heightened in hyperglycaemia. MGO plasma levels are two-fold to five-fold increased in diabetics and its accumulation promotes the progression of vascular complications. Impairment of endothelium-derived nitric oxide represents a common feature of endothelial dysfunction in diabetics. We previously demonstrated that MGO induces endothelial insulin resistance. Increasing evidence shows that high glucose and MGO modify vascular expression of several microRNAs (miRNAs), suggesting their potential role in the impairment of endothelial insulin sensitivity. The aim of the study is to investigate whether miRNAs may be involved in MGO-induced endothelial insulin resistance in endothelial cells.MGO reduces the expression of miR-190a both in mouse aortic endothelial cells (MAECs) and in aortae from mice knocked-down for glyoxalase-1. miR-190a inhibition impairs insulin sensitivity, whereas its overexpression prevents the MGO-induced insulin resistance in MAECs. miR-190a levels are not affected by the inhibition of ERK1/2 phosphorylation. Conversely, ERK1/2 activation is sustained by miR-190a inhibitor and the MGO-induced ERK1/2 hyper-activation is reduced by miR-190a mimic transfection. Similarly, protein levels of the upstream KRAS are increased by both MGO and miR-190a inhibitor, and these levels are reduced by miR-190a mimic transfection. Interestingly, silencing of KRAS is able to rescue the MGO-impaired activation of IRS1/Akt/eNOS pathway in response to insulin.In conclusion, miR-190a down-regulation plays a role in MGO-induced endothelial insulin resistance by increasing KRAS. This study highlights miR-190a as new candidate for the identification of strategies aiming at ameliorating vascular function in diabetes.

Short-term effects of low-dose estradiol on endothelial function and blood viscosity in nondiabetic postmenopausal overweight women: a double-blind, placebo-controlled study.

The beneficial effects of estrogen on endothelial function depend on its integrity. This study evaluates the short-term effects of low-dose transdermal estradiol on endothelial function, insulin sensitivity, and blood viscosity in nondiabetic overweight/obese women. Forty-four nondiabetic overweight/obese women with a history of recent menopause were randomly allocated, in a double-blind fashion, to receive transdermal estradiol (1 mg/d, n = 22) or placebo (n = 22). The following parameters were assessed: endothelial reactivity (venous occlusion plethysmography and nailfold videocapillaroscopy), plasma levels of soluble adhesion molecules, insulin sensitivity (homeostasis model assessment of insulin resistance and areas under the curve of insulin and glucose during an oral glucose tolerance test), and blood and plasma viscosity. Data were expressed as means ± SD or medians [first to third quartiles]. Participants were aged 51.8 ± 2.3 years with a body mass index of 31.5 ± 2.5 kg/m and time since menopause was 3 [2-5] years. At baseline, no differences between the groups were observed; however, after 3 months of treatment, the following changes were observed in the estradiol group compared with the placebo group: a decrease in the forearm vascular resistance at baseline (36.37 [24.9-51.27] vs 51.3 [40.88-70.03] mm Hg/mL per min 100 mL tissue, P < 0.01) and during the postocclusive reactive hyperemia response (15.93 [11.32-22.29] vs 22.13 [16.46-29.7] mm Hg/mL per min 100 mL tissue, P < 0.01), and an increase in red blood cell velocity at rest (0.316 [0.309-0.326] vs 0.303 [0.293-0.308] mm/s, P < 0.001) and during postocclusive reactive hyperemia response (0.374 [0.353-0.376] vs 0.341 [0.333-0.355] mm/s, P < 0.001). Furthermore, blood viscosity was lower in the estradiol group than in the placebo group (3.57 ± 0.12 vs 3.76 ± 0.22 mPa.s; P < 0.01). Short-term use of low-dose transdermal estradiol in nondiabetic overweight/obese women with a history of recent menopause improved endothelial function and decreased blood viscosity compared with placebo.

Evaluation of endothelial function and insulin sensitivity in patients with prolactinoma

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

SIRT3 Deficiency Induces Endothelial Insulin Resistance and Blunts Endothelial-Dependent Vasorelaxation in Mice and Human with Obesity.

Recent evidence implicates the critical role of Sirtuin 3 (SIRT3) in the development of many metabolic diseases, but the contribution of SIRT3 to vascular homeostasis remains largely unknown. The aim of this study was to investigate the role of SIRT3 in endothelial insulin resistance and vascular dysfunction in obesity. We found an impaired insulin-induced mesenteric vasorelaxation and concomitant reduced vascular SIRT3 expression in morbid obese human subjects compared with the non-obese subjects. Downregulation of SIRT3 in cultured human endothelial cells increased mitochondrial reactive oxygen species (mtROS) and impaired insulin signaling as evidenced by decreased phosphorylation of Akt and endothelial nitric oxide synthase and subsequent reduced nitric oxide (NO) release. In addition, obese mice induced by 24-week high-fat diet (HFD) displayed an impaired endothelium-dependent vasorelaxation to both insulin and acetylcholine, which was further exacerbated by the gene deletion of Sirt3. Scavenging of mtROS not only restored insulin-stimulated NO production in SIRT3 knockdown cells, but also improved insulin-induced vasorelaxation in SIRT3 knockout mice fed with HFD. Taken together, our findings suggest that SIRT3 positively regulates endothelial insulin sensitivity and show that SIRT3 deficiency and resultant increased mtROS contribute to vascular dysfunction in obesity.

Telmisartan w leczeniu nadciśnienia tętniczego — optymalny wybór zgodny z wytycznymi Polskiego Towarzystwa Nadciśnienia Tętniczego z 2015 roku

In recent years emphasis in the treatment of hypertension has been put on the individualization of treatment. The recently published guidelines of the Polish Society of Hypertension list several clinical situations in which use of angiotensin II receptor blockers (ARBs) is indicated. Blockade of the renin-angiotensin- aldosterone system plays a pivotal role in the treatment of high blood pressure and prevention of target organ damage. Telmisartan is an angiotensin II receptor blocker displaying beneficial unique pharmacologic properties, metabolic effects, antihypertensive efficacy in monotherapy and combinations and good tolerance. Clinical studies confirm that telmisartan improves endothelial function, insulin sensitivity and lipid profiles, reduces arterial stiffness. In addition, telmisartan improves renal function and has potential beneficial effects on prevention of cerebrovascular disease. The Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) study has shown that telmisartan provides similar cardiovascular protection to ramipril in high-risk patients, while being better tolerated.

Abstract 13492: Increasing Endothelial Insulin Sensitivity Rescues Vascular Function and Repair in Systemic Insulin Resistance by Restoring Nitric Oxide Bioavailability and Improving Endothelial Cell Migration

Introduction: Insulin resistance is independently associated with vascular disease. Insulin receptor haploinsufficient (IRKO) mice are hypertensive and exhibit endothelial dysfunction and impaired vascular repair despite normal glucoregulation. We hypothesise that endothelial insulin signalling is crucial for vascular function and that selectively restoring endothelial cell (EC) insulin signalling may rescue these vascular derangements. Methods: Transgenic mice with Tie-2-driven human IR expression in the endothelium (HIRECO) were bred with IRKO, providing HIRECOxIRKO (HxI) offspring. Metabolic assessment included glucose and insulin tolerance tests, ELISA for plasma insulin concentration and non-invasive blood pressure measurement. Femoral artery injury was performed with angioplasty wires; repair was quantified in Evans Blue-perfused vessels at day 4. Circulating endothelial progenitor cells (EPC) were counted using FACS and cultured from blood. Explanted aortic rings were exposed to phenylephrine (PE) before and after incubation with the NOS inhibitor L-NMMA in organ baths to assess vasomotor function. Boyden chamber assays were used to assess migration of cultured lung ECs to VEGF. Data are expressed as mean(SE) and compared using t-tests;*=p&lt;0.05. Results: HxI and IRKO had similar glucocompetence and basal insulin [0.8(0.1)ng/mL vs 0.7(0.2);p=0.8]. Systolic BP was lower in HxI [97(2)mmHg vs 106(3)*]. Vascular repair was improved in HxI [57(4)% vs 46(2)%*]. There was no recovery in EPC numbers by FACS [99(10) vs 105(15);p=0.74], nor in culture [0.4(0.1)/HPF vs 0.4(0.2);p=0.99]. HxI aortic rings showed less PE-induced constriction than IRKO [EC50 8.9(0.8)x10 7 nM vs 6.3(0.9)x10 7 *], with greater NO bioavailability [Post-L-NMMA PE EC50 4.1(0.8)x10 7 nM vs IRKO 6.1(1.8)x10 7 *]. ECs from HxI showed greater net migration to VEGF [6.3(1.3) vs 1.9(1.2)*]. Conclusion: HIRECOxIRKO show rescue of vascular function despite global insulin resistance. This is not associated with improved glucoregulation or EPC abundance; rather, it may relate to increased NO availability and enhanced EC migration. Our data support endothelial insulin sensitisation as a potential therapeutic target for vascular dysfunction in insulin resistance.

Vascular and metabolic effects of the haem oxygenase-1 inducer haem arginate in subjects with the metabolic syndrome: A translational cross-over study.

This translational randomized and vehicle-controlled cross-over study was performed to assess the impact of haem arginate treatment on haem oxygenase-1 induction, endothelial function and insulin sensitivity in subjects with the metabolic syndrome (n = 14). Both treatment periods consisted of 5 days. Haem arginate or vehicle (l-arginine) was administered intravenously on Days 1 and 3. Forearm blood flow in response to acetylcholine and nitroglycerine was measured by venous occlusion plethysmography (Day 3), insulin sensitivity by a hyperinsulinaemic clamp procedure (Day 5). Haem arginate did not improve endothelial function or insulin sensitivity but significantly reduced the vasodilator response to nitroglycerine (p < 0.01). These negative findings are in contrast to the preclinical data, which may be due to short duration of therapy and limited haem oxygenase-1 induction as well as interference by markedly elevated plasma haem levels observed after haem arginate treatment (p < 0.01). Future studies should pay attention to the delicate balance between sufficient dosing and timely normalization of plasma haem levels.

Abstract 089: CD36 Genetic Variant Impacts Nitric Oxide Regulation of Endothelial Function: Response to Chronic Treatment with Phosphodiesterase 5 Inhibition

CD36, a scavenger receptor expressed on endothelial cells, interacts with thrombospodin-1, a matrix protein that modulates nitric oxide-soluble guanylate cyclase (NO-sGC) signaling. CD36 genetic variants associate with endothelial dysfunction, atherosclerosis, hypertension and insulin resistance. A coding variant of CD36 (rs3211938, G/T genotype) that causes partial CD36 deficiency (50% reduction) is common (~18%) in African Americans (AA); however, it is unknown, if this genotype influences NO-dependent endothelial function. This study examined whether potentiating NO-sGC pathways with the phosphodiesterase 5 inhibitor, sildenafil citrate, improves endothelial function and insulin sensitivity in AA women with or without the G/T genotype. Forty-six AA women with metabolic syndrome (MetS) participated in a 4-week, parallel-arm, double-blind, and placebo-controlled study. Carefully matched subjects were randomly assigned to sildenafil citrate 20 mg TID versus placebo; sildenafil (n= 23, 42±10 years old, BMI 39±5 kg/m2, fasting insulin 15±8 uU/ml) and placebo (n=23, age 43±10, BMI 39±6 kg/m2, fasting insulin 14±10 uU/ml). Primary endpoints were insulin sensitivity and endothelial function measured by intravenous glucose tolerance test and flow mediated dilation, respectively. Treatment compliance was documented with plasma sildenafil levels (mean 57±50 ng/ml). There was no difference in insulin sensitivity (p=0.676) or flow-mediated dilation (p=0.649) between intervention groups. However, subgroup analyses showed a significant interaction between sildenafil citrate treatment and G/T genotype (p=0.018). Sildenafil citrate improved endothelial function in G/T carriers (the mean difference: 2.9, the 95% CI: -0.90 to 6.8, p = 0.126) and decreased endothelial function in T/T carriers (the mean difference: -2.6, the 95% CI: -5.1 to -0.1, p = 0.040). We conclude that the rs3211938 common CD36 genetic variant influences NO-dependent endothelial function in response to chronic treatment with phosphodiesterase 5 inhibition. Further studies are needed to determine if rs3211938 and other common CD36 genotypes influence endothelial function and the inter-individual variability in response to the drug.

High Trans‐Fat but not Saturated Fat Beverage Causes an Acute Reduction in Vascular Endothelial Function and Insulin Sensitivity in Humans

A diet high in trans‐fatty acids (TFA) is associated with increased cardiovascular disease risk, mediated in part from dyslipidemia, endothelial dysfunction and insulin resistance. A high‐fat meal causes a transient (3‐4 hrs postprandial) reduction in endothelial function and insulin sensitivity, but studies are often confounded by meals high in carbohydrate, saturated fatty acids (SFAs) and/or TFAs. We hypothesized that a beverage high in TFA (but low in carbohydrate, SFA) would cause a larger acute reduction in endothelial function (brachial artery flow‐mediated dilation, FMD) and insulin sensitivity compared with SFA (but low in carbohydrate, TFA). Healthy non‐obese adults (n=11; 9M/2F; age=47±3 yrs) ingested a warm beverage (520kcal, 56g total fat, 5g carbohydrate), high in either TFA (42%TFA, 23%SFA; partially hydrogenated soybean oil), SFA (88%SFA, 0.2%TFA; coconut oil) or placebo (2g total fat, 5g carbohydrate) in a randomized, cross‐over study. TFA (0.19±0.02 to 0.06±0.03mm, P&lt;0.01), but not SFA (0.14±0.03 vs. 0.11±0.04mm, P=0.49) or placebo (0.08±0.04 to 0.062±0.03mm, P=0.52), caused a reduction in FMD at 3‐4 hours (P&lt;0.01 for time; p=0.02 for interaction effects). Postprandial glucose was reduced across groups (P&lt;0.001), whereas the homeostasis model of insulin resistance (HOMA‐IR) decreased in SFA and placebo (P&lt;0.001) but not TFA (1.4±0.2 vs 1.2±0.2, P=0.08, interaction P=0.02). These data suggest that ingestion of a beverage high in TFA, but not SFA, results in an acute reduction in endothelial function and insulin sensitivity in healthy adults. Supported by NIH 5T32HL007638‐28, 5T32HL007121‐3, U54TR001013.

Endothelial function and insulin sensitivity during acute non-esterified fatty acid elevation: Effects of fat composition and gender

Background and aimsWe have reported that adverse effects on flow-mediated dilation of an acute elevation of non-esterified fatty acids rich in saturated fat (SFA) are reversed following addition of long-chain (LC) n-3 polyunsaturated fatty acids (PUFA), and hypothesised that these effects may be mediated through alterations in insulin signalling pathways. In a subgroup, we explored the effects of raised NEFA enriched with SFA, with or without LC n-3 PUFA, on whole body insulin sensitivity (SI) and responsiveness of the endothelium to insulin infusion. Methods and resultsThirty adults (mean age 27.8 y, BMI 23.2 kg/m2) consumed oral fat loads on separate occasions with continuous heparin infusion to elevate NEFA between 60 and 390 min. For the final 150 min, a hyperinsulinaemic-euglycaemic clamp was performed, whilst FMD and circulating markers of endothelial function were measured at baseline, pre-clamp (240 min) and post-clamp (390 min). NEFA elevation during the SFA-rich drinks was associated with impaired FMD (P = 0.027) whilst SFA + LC n-3 PUFA improved FMD at 240 min (P = 0.003). In males, insulin infusion attenuated the increase in FMD with SFA + LC n-3 PUFA (P = 0.049), with SI 10% greater with SFA + LC n-3 PUFA than SFA (P = 0.041). ConclusionThis study provides evidence that NEFA composition during acute elevation influences both FMD and SI, with some indication of a difference by gender. However our findings are not consistent with the hypothesis that the effects of fatty acids on endothelial function and SI operate through a common pathway.This trial was registered at clinical trials.gov as NCT01351324 on 6th May 2011.

The glucocorticoid receptor requires pro-inflammatory signaling to protect from lung inflammation and high fat diet induced insulin resistance

Glucocorticoids (GCs) are widely used to treat inflammatory diseases, but also shape a plethora of physiological responses including glucose homeostasis. Now we show that the GC receptor (GR) expression in macrophages requires pro-inflammatory signaling to upregulate synergistically sphingosine kinase 1 (SphK1), a gene involved in endothelial barrier regulation and insulin sensitivity, which we found essential to limit acute lung injury (ALI) and alleviate insulin resistance.

ENDOTHELIAL-SPECIFIC OVEREXPRESSION OF MUTATED INSULIN-LIKE GROWTH FACTOR-1 RECEPTORS (IGF-1R) ENHANCES ENDOTHELIAL INSULIN SENSITIVITY AND VASCULAR HYDROGEN PEROXIDE GENERATION

Expression of Insulin-like growth factor-1 receptor (IGF-1R) and hybrid receptors formed between IGF-1R and insulin receptor (IR) in the vascular endothelium may be contributing factors to initiation of insulin resistance. The hypothesis that the IGF-1R acts as a negative regulator of insulin sensitivity and NO bioavailability in the endothelium is further investigated. Mice expressing non-functional, mutated human IGF-1R (K1003R) on the vascular endothelium (mIGFREO) under the control of Tie2 promoter-enhancer were generated. mIGFREO demonstrated no significant abnormalities in body and organ weight, as well as blood pressure compared to the wild type (WT) littermates. mIGFREO mice demonstrated preserved glucoregulation but showed a significant enhancement of whole body insulin sensitivity. Total hybrid expression was increased in the mIGFREO endothelial cells compared to WT controls, as well as the activated tyrosine phosphorylated insulin receptor (IRpY1328). Free fatty acid levels were lower in mIGFREO mice compared to WT littermates. Endothelial function assessed by vasorelaxation of aorta to acetylcholine remained unchanged between mIGFREO and WT littermates. The basal level of eNOS phosphorylation was enhanced in the mIGFREO endothelial cells compared to WT littermates. Nevertheless, mIGFREO aorta was significantly resistant to the vasodilatory effect of insulin. Interestingly, superoxide anion production was decreased among the mIGFREO mice compared to the WT littermate controls. Protein ex pression of NOX2, a source of superoxide anion generation was found to be significantly reduced, with a concomitant increase in NOX4 expression. These data suggest that mutation of endothelial IGF-1R demonstrates divergent effects on whole body and vascular endothelial insulin sensitivity.