Insulin inhibits the expression of intercellular adhesion molecule-1 by human aortic endothelial cells through stimulation of nitric oxide

Outpatient insulin use in type 2 diabetes mellitus and acute respiratory distress syndrome outcomes: A retrospective cohort study

BACKGROUND

The impact of type 2 diabetes mellitus (T2DM) on acute respiratory distress syndrome (ARDS) is debatable. T2DM was suspected to reduce the risk and complications of ARDS. However, during coronavirus disease 2019 (COVID-19), T2DM predisposed patients to ARDS, especially those who were on insulin at home.

AIM

To evaluate the impact of outpatient insulin use in T2DM patients on non-COVID-19 ARDS outcomes.

METHODS

We conducted a retrospective cohort analysis using the Nationwide Inpatient Sample database. Adult patients diagnosed with ARDS were stratified into insulin-dependent diabetes mellitus (DM) (IDDM) and non-insulin-dependent DM (NIDDM) groups. After applying exclusion criteria and matching over 20 variables, we compared cohorts for mortality, duration of mechanical ventilation, incidence of acute kidney injury (AKI), length of stay (LOS), hospitalization costs, and other clinical outcomes.

RESULTS

Following 1:1 propensity score matching, the analysis included 274 patients in each group. Notably, no statistically significant differences emerged between the IDDM and NIDDM groups in terms of mortality rates (32.8% vs 31.0%, P = 0.520), median hospital LOS (10 d, P = 0.537), requirement for mechanical ventilation, incidence rates of sepsis, pneumonia or AKI, median total hospitalization costs, or patient disposition upon discharge.

CONCLUSION

Compared to alternative anti-diabetic medications, outpatient insulin treatment does not appear to exert an independent influence on in-hospital morbidity or mortality in diabetic patients with non-COVID-19 ARDS.

Inflammation and vascular dysfunction: The negative synergistic combination of diabetes and COVID-19

AIMS

Several reports indicate that diabetes determines an increased mortality risk in patients with coronavirus disease 19 (COVID-19) and a good glycaemic control appears to be associated with more favourable outcomes. Evidence also supports that COVID-19 pneumonia only accounts for a part of COVID-19 related deaths. This disease is indeed characterised by abnormal inflammatory response and vascular dysfunction, leading to the involvement and failure of different systems, including severe acute respiratory distress syndrome, coagulopathy, myocardial damage and renal failure. Inflammation and vascular dysfunction are also well-known features of hyperglycemia and diabetes, making up the ground for a detrimental synergistic combination that could explain the increased mortality observed in hyperglycaemic patients.

MATERIALS AND METHODS

In this work, we conduct a narrative review on this intriguing connection. Together with this, we also present the clinical characteristics, outcomes, laboratory and histopathological findings related to this topic of a cohort of nearly 1000 subjects with COVID-19 admitted to a third-level Hospital in Milan.

RESULTS

We found an increased mortality in subjects with COVID-19 and diabetes, together with an altered inflammatory profile.

CONCLUSIONS

This may support the hypothesis that diabetes and COVID-19 meet at the crossroads of inflammation and vascular dysfunction. (ClinicalTrials.gov NCT04463849 and NCT04382794).

Mapping the dynamics of insulin-responsive pathways in the blood-brain barrier endothelium using time-series transcriptomics data

Critical functions of the blood-brain barrier (BBB), including cerebral blood flow, energy metabolism, and immunomodulation, are regulated by insulin signaling pathways. Therefore, endothelial insulin resistance could lead to BBB dysfunction, which is associated with neurodegenerative diseases such as Alzheimer's disease (AD). The current study aims to map the dynamics of insulin-responsive pathways in polarized human cerebral microvascular endothelial cell (hCMEC/D3) monolayers. RNA-Sequencing was performed on hCMEC/D3 monolayers with and without insulin treatment at various time points. The Short Time-series Expression Miner (STEM) method was used to identify gene clusters with distinct and representative expression patterns. Functional annotation and pathway analysis of genes from selected clusters were conducted using Webgestalt and Ingenuity Pathway Analysis (IPA) software. Quantitative expression differences of 16,570 genes between insulin-treated and control monolayers were determined at five-time points. The STEM software identified 12 significant clusters with 6880 genes that displayed distinct temporal patterns upon insulin exposure, and the clusters were further divided into three groups. Gene ontology (GO) enrichment analysis demonstrated that biological processes protecting BBB functions such as regulation of vascular development and actin cytoskeleton reorganization were upregulated after insulin treatment (Group 1 and 2). In contrast, GO pathways related to inflammation, such as response to interferon-gamma, were downregulated (Group 3). The IPA analyses further identified insulin-responsive cellular and molecular pathways that are associated with AD pathology. These findings unravel the dynamics of insulin action on the BBB endothelium and inform about downstream signaling cascades that are potentially disrupted due to brain insulin resistance prevalent in AD.

Intranasal insulin and orexins to treat age-related cognitive decline

The intranasal (IN) administration of neuropeptides, such as insulin and orexins, has been suggested as a treatment strategy for age-related cognitive decline (ARCD). Because dysfunctional neuropeptide signaling is an observed characteristic of ARCD, it has been suggested that IN delivery of insulin and/or orexins may restore endogenous peptide signaling and thereby preserve cognition. IN administration is particularly alluring as it is a relatively non-invasive method that directly targets peptides to the brain. Several laboratories have examined the behavioral effects of IN insulin in young, aged, and cognitively impaired rodents and humans. These studies demonstrated improved performance on various cognitive tasks following IN insulin administration. Fewer laboratories have assessed the effects of IN orexins; however, this peptide also holds promise as an effective treatment for ARCD through the activation of the cholinergic system and/or the reduction of neuroinflammation. Here, we provide a brief overview of the advantages of IN administration and the delivery pathway, then summarize the current literature on IN insulin and orexins. Additional preclinical studies will be useful to ultimately uncover the mechanisms underlying the pro-cognitive effects of IN insulin and orexins, whereas future clinical studies will aid in the determination of the most efficacious dose and dosing paradigm. Eventually, IN insulin and/or orexin administration may be a widely used treatment strategy in the clinic for ARCD.

Pregnancies in Diabetes and Obesity: The Capacity-Load Model of Placental Adaptation

Excess nutritional supply to the growing fetus, resulting from maternal diabetes and obesity, is associated with increased risks of fetal maldevelopment and adverse metabolic conditions in postnatal life. The placenta, interposed between mother and fetus, serves as the gateway between the two circulations and is usually considered to mediate maternal exposures to the fetus through a direct supply line. In this Perspective, however, we argue that the placenta is not an innocent bystander and mounts responses to fetal "signals of distress" to sustain its own adequate function and protect the fetus. We describe several types of protection that the placenta can offer the fetus against maternal metabolic perturbations and offer a theoretical model of how the placenta responds to the intrauterine environment in maternal diabetes and obesity to stabilize the fetal environment. Our approach supports growing calls for early screening and control of pregnancy metabolism to minimize harmful fetal outcomes.

Dysregulation of Leukocyte Trafficking in Type 2 Diabetes: Mechanisms and Potential Therapeutic Avenues

Type 2 Diabetes Mellitus (T2DM) is a chronic inflammatory disorder that is characterized by chronic hyperglycemia and impaired insulin signaling which in addition to be caused by common metabolic dysregulations, have also been associated to changes in various immune cell number, function and activation phenotype. Obesity plays a central role in the development of T2DM. The inflammation originating from obese adipose tissue develops systemically and contributes to insulin resistance, beta cell dysfunction and hyperglycemia. Hyperglycemia can also contribute to chronic, low-grade inflammation resulting in compromised immune function. In this review, we explore how the trafficking of innate and adaptive immune cells under inflammatory condition is dysregulated in T2DM. We particularly highlight the obesity-related accumulation of leukocytes in the adipose tissue leading to insulin resistance and beta-cell dysfunction and resulting in hyperglycemia and consequent changes of adhesion and migratory behavior of leukocytes in different vascular beds. Thus, here we discuss how potential therapeutic targeting of leukocyte trafficking could be an efficient way to control inflammation as well as diabetes and its vascular complications.

Carpinus turczaninowii extract modulates arterial inflammatory response: a potential therapeutic use for atherosclerosis

BACKGROUND/OBJECTIVES

Vascular inflammation is an important feature in the atherosclerotic process. Recent studies report that leaves and branches of Carpinus turczaninowii (C. turczaninowii) have antioxidant capacity and exert anti-inflammatory effects. However, no study has reported the regulatory effect of C. turczaninowii extract on the arterial inflammatory response. This study therefore investigated modulation of the arterial inflammatory response after exposure to C. turczaninowii extract, using human aortic vascular smooth muscle cells (HAoSMCs).

MATERIALS/METHODS

Scavenging activity of free radicals, total phenolic content (TPC), cell viability, mRNA expressions, and secreted levels of cytokines were measured in LPS-stimulated (10 ng/mL) HAoSMCs treated with the C. turczaninowii extract.

RESULTS

C. turczaninowii extract contains high amounts of TPC (225.6 ± 21.0 mg of gallic acid equivalents/g of the extract), as well as exerts time-and dose-dependent increases in strongly scavenged free radicals (average 14.8 ± 1.97 µg/mL IC₅₀ at 40 min). Cell viabilities after exposure to the extracts (1 and 10 µg/mL) were similar to the viability of non-treated cells. Cytokine mRNA expressions were significantly suppressed by the extracts (1 and 10 µg/mL) at 6 hours (h) after exposure. Interleukin-6 secretion was dose-dependently suppressed 2 h after incubation with the extract, at 1–10 µg/mL in non-stimulated cells, and at 5 and 10 µg/mL in LPS-stimulated cells. Similar patterns were also observed at 24 h after incubation with the extract (at 1–10 µg/mL in non-stimulated cells, and at 10 µg/mL in the LPS-stimulated cells). Soluble intracellular vascular adhesion molecules (sICAM-1) secreted from non-stimulated cells and LPS-stimulated cells were similarly suppressed in a dose-dependent manner after 24 h exposure to the extracts, but not after 2 h. In addition, sICAM-1 concentration after 24 h treatment was positively related to IL-6 levels after 2 h and 24 h exposure (r = 0.418, P = 0.003, and r = 0.524, P < 0.001, respectively).

CONCLUSIONS

This study demonstrates that C. turczaninowii modulates the arterial inflammatory response, and indicates the potential to be applied as a therapeutic use for atherosclerosis.

Adipose Tissue Dysfunction Occurs Independently of Obesity in Adipocyte-Specific Oncostatin Receptor Knockout Mice

OBJECTIVE

This study examined the phenotypic effects of adipocyte-specific oncostatin M receptor (OSMR) loss in chow-fed mice.

METHODS

Chow-fed adipocyte-specific OSMR knockout (FKO) mice and littermate OSMR^fl/fl controls were studied. Tissue weights, insulin sensitivity, adipokine production, and stromal cell immunophenotypes were assessed in epididymal fat (eWAT); serum adipokine production was also assessed. In vitro, adipocytes were treated with oncostatin M, and adipokine gene expression was assessed.

RESULTS

Body weights, fasting blood glucose levels, and eWAT weights did not differ between genotypes. However, the eWAT of OSMR^FKO mice was modestly less responsive to insulin stimulation than that of OSMR^fl/fl mice. Notably, significant increases in adipokines, including C-reactive protein, lipocalin 2, intercellular adhesion molecule-1, and insulinlike growth factor binding protein 6, were observed in the eWAT of OSMR^FKO mice. In addition, significant increases in fetuin A and intercellular adhesion molecule-1 were detected in OSMR^FKO serum. Flow cytometry revealed a significant increase in leukocyte number and modest, but not statistically significant, increases in B cells and T cells in the eWAT of OSMR^FKO mice.

CONCLUSIONS

The chow-fed OSMR^FKO mice exhibited adipose tissue dysfunction and increased proinflammatory adipokine production. These results suggest that intact adipocyte oncostatin M-OSMR signaling is necessary for adipose tissue immune cell homeostasis.

Ageing: Is there a role for arachidonic acid and other bioactive lipids? A review

Ageing is inevitable. Recent studies suggest that it could be delayed. Low-grade systemic inflammation is seen in type 2 diabetes mellitus, hypertension and endothelial dysfunction that are common with increasing age. In all these conditions, an alteration in arachidonic acid (AA) metabolism is seen in the form of increased formation of pro-inflammatory eicosanoids and decreased production of anti-inflammatory lipoxins, resolvins, protectins and maresins and decreased activity of desaturases. Calorie restriction, exercise and parabiosis delay age-related changes that could be related to enhanced proliferation of stem cells, decrease in inflammation and transfer of GDF-11 (growth differentiation factor-11) and other related molecules from the young to the old, increase in the formation of lipoxin A4, resolvins, protectins and maresins, hydrogen sulfide (H2S) and nitric oxide (NO); inhibition of ageing-related hypothalamic or brain IKK-β and NF-kB activation, decreased gonadotropin-releasing hormone (GnRH) release resulting in increased neurogenesis and consequent decelerated ageing. This suggests that hypothalamus participates in ageing process. N-acylethanolamines (NAEs) and lipid-derived signalling molecules can be tuned favorably under dietary restriction to extend lifespan and/or prevent advanced age associated diseases in an mTOR dependent pathway manner. Sulfur amino acid (SAA) restriction increased hydrogen sulfide (H2S) production and protected tissues from hypoxia and tissue damage. Anti-inflammatory metabolites formed from AA such as LXA4, resolvins, protectins and maresins enhance production of NO, CO, H2S; suppress NF-kB expression and alter mTOR expression and thus, may aid in delaying ageing process. Dietary restriction and exercise enhance AA metabolism to form LXA4, resolvins, protectins and maresins that have anti-inflammatory actions. AA and their metabolites also influence stem cell biology, enhance neurogenesis to improve memory and augment autophagy to prolong life span. Thus, AA and other PUFAs and their anti-inflammatory metabolites inhibit inflammation, augment stem cell proliferation, restore to normal lipid-derived signaling molecules and NO and H2S production, enhance autophagy and prolong life span.

Vascular Cell Adhesion Molecule 1, Intercellular Adhesion Molecule 1, and Cluster of Differentiation 146 Levels in Patients with Type 2 Diabetes with Complications

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a multisystemic, chronic disease accompanied by microvascular complications involving various complicated mechanisms. Intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and cluster of differentiation-146 (CD146) are mainly expressed by endothelial cells, and facilitate the adhesion and transmigration of immune cells, leading to inflammation. In the present study, we evaluated the levels of soluble adhesion molecules in patients with microvascular complications of T2DM.

METHODS

Serum and whole blood samples were collected from 58 T2DM patients with microvascular complications and 20 age-matched healthy subjects. Levels of soluble ICAM-1 (sICAM-1) and soluble VCAM-1 (sVCAM-1) were assessed using enzyme-linked immunosorbent assay, while flow cytometry was used to determine CD146 levels.

RESULTS

Serum sICAM-1 levels were lower in T2DM patients with microvascular complications than in healthy controls (P<0.05). No significant differences were found in sVCAM-1 and CD146 levels between the study and the control group. Although patients were subdivided into groups according to the type of microvascular complications that they experienced, cell adhesion molecule levels were not correlated with the complication type.

CONCLUSION

In the study group, most of the patients were on insulin therapy (76%), and 95% of them were receiving angiotensin-converting enzyme (ACE)-inhibitor agents. Insulin and ACE-inhibitors have been shown to decrease soluble adhesion molecule levels via various mechanisms, so we suggest that the decreased or unchanged levels of soluble forms of cellular adhesion molecules in our study group may have resulted from insulin and ACE-inhibitor therapy, as well as tissue-localized inflammation in patients with T2DM.

The association between blood glucose levels and matrix-metalloproteinase-9 in early severe sepsis and septic shock

Background

Hyperglycemia is a frequent and important metabolic derangement that accompanies severe sepsis and septic shock. Matrix-Metalloproteinase 9 (MMP-9) has been shown to be elevated in acute stress hyperglycemia, chronic hyperglycemia, and in patient with sepsis. The objective of this study was to examine the clinical and pathogenic link between MMP-9 and blood glucose (BG) levels in patients with early severe sepsis and septic shock.

Methods

We prospectively examined 230 patients with severe sepsis and septic shock immediately upon hospital presentation and before any treatment including insulin administration. Clinical and laboratory data were obtained along with blood samples for the purpose of this study. Univariate tests for mean and median distribution using Spearman correlation and analysis of variance (ANOVA) were performed. A p value ≤ 0.05 was considered statistically significant.

Results

Patients were grouped based on their presenting BG level (mg/dL): BG <80 (n = 32), 80–120 (n = 53), 121–150 (n = 38), 151–200 (n = 23), and > 201 (n = 84). Rising MMP-9 levels were significantly associated with rising BG levels (p = 0.043). A corresponding increase in the prevalence of diabetes for each glucose grouping from 6.3 to 54.1 % (p = 0.0001) was also found. As MMP-9 levels increased a significantly (p < 0.001) decreases in IL-8 (pg/mL) and ICAM-1 (ng/mL) were noted.

Conclusion

This is the first study in humans demonstrating a significant and early association between MMP-9 and BG levels in in patients with severe sepsis and septic shock. Neutrophil affecting biomarkers such as IL-8 and ICAM-1 are noted to decrease as MMP-9 levels increase. Clinical risk stratification using MMP-9 levels could potentially help determine which patients would benefit from intensive versus conventional insulin therapy. In addition, antagonizing the up-regulation of MMP-9 could serve as a potential treatment option in severe sepsis or septic shock patients.

Pulsatile Hyperglycaemia Induces Vascular Oxidative Stress and GLUT 1 Expression More Potently than Sustained Hyperglycaemia in Rats on High Fat Diet

INTRODUCTION

Pulsatile hyperglycaemia resulting in oxidative stress may play an important role in the development of macrovascular complications. We investigated the effects of sustained vs. pulsatile hyperglycaemia in insulin resistant rats on markers of oxidative stress, enzyme expression and glucose metabolism in liver and aorta. We hypothesized that liver's ability to regulate the glucose homeostasis under varying states of hyperglycaemia may indirectly affect oxidative stress status in aorta despite the amount of glucose challenged with.

METHODS

Animals were infused with sustained high (SHG), low (SLG), pulsatile (PLG) glucose or saline (VEH) for 96 h. Oxidative stress status and key regulators of glucose metabolism in liver and aorta were investigated.

RESULTS

Similar response in plasma lipid oxidation was observed in PLG as in SHG. Likewise, in aorta, PLG and SHG displayed increased expression of glucose transporter 1 (GLUT1), gp-91PHOX and super oxide dismutase (SOD), while only the PLG group showed increased accumulation of oxidative stress and oxidised low density lipoprotein (oxLDL) in aorta.

CONCLUSION

Pulsatile hyperglycaemia induced relatively higher levels of oxidative stress systemically and in aorta in particular than overt sustained hyperglycaemia thus supporting the clinical observations that pulsatile hyperglycaemia is an independent risk factor for diabetes related macrovascular complications.

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.

Intranasal Insulin and Insulin-Like Growth Factor 1 as Neuroprotectants in Acute Ischemic Stroke

Treatment options for stroke remain limited. Neuroprotective therapies, in particular, have invariably failed to yield the expected benefit in stroke patients, despite robust theoretical and mechanistic background and promising animal data. Insulin and insulin-like growth factor 1 (IGF-1) play a pivotal role in critical brain functions, such as energy homeostasis, neuronal growth, and differentiation. They may exhibit neuroprotective properties in acute ischemic stroke based upon their vasodilatory, anti-inflammatory and antithrombotic effects, as well as improvements of functional connectivity, neuronal metabolism, neurotransmitter regulation, and remyelination. Intranasally administered insulin has demonstrated a benefit for prevention of cognitive decline in older people, and IGF-1 has shown potential benefit to improve functional outcomes in animal models of acute ischemic stroke. The intranasal route presents a feasible, tolerable, safe, and particularly effective administration route, bypassing the blood-brain barrier and maximizing distribution to the central nervous system (CNS), without the disadvantages of systemic side effects and first-pass metabolism. This review summarizes the neuroprotective potential of intranasally administered insulin and IGF-1 in stroke patients. We present the theoretical background and pathophysiologic mechanisms, animal and human studies of intranasal insulin and IGF-1, and the safety and feasibility of intranasal route for medication administration to the CNS.

Use of insulin to decrease septic shock-induced myocardial depression in a porcine model

Insulin is known to attenuate septic shock-induced myocardial depression. Possible mechanisms include an anti-inflammatory or inotropic effect of insulin. The objective of this study was to determine whether the mechanism of action of insulin in attenuating septic shock-induced myocardial depression is through an immunomodulatory effect. Fourteen pigs were assigned to one of two groups. Both groups received a 4-h infusion of lipopolysaccharide endotoxin from Escherichia coli 0111:B4. Group 2 additionally received insulin at 1.5 U/kg/h with infusions of D50 normal saline and KCl to maintain normal serum glucose and potassium levels. Cardiac function was measured with shortening fraction using transthoracic echocardiogram. Plasma TNF-α, IL-1β, and IL-6 levels were obtained every 30 min. Postmortem cytokine analysis and histomorphology were performed on the heart tissue. Although insulin attenuated septic shock-induced myocardial depression, this was not due to an anti-inflammatory effect and, therefore, likely resulted from an inotropic effect of insulin.

Glycemia-dependent nuclear factor κB activation contributes to mechanical allodynia in rats with chronic postischemia pain

BACKGROUND

Ischemia-reperfusion injury causes chronic postischemia pain (CPIP), and rats with higher glycemia during ischemia-reperfusion injury exhibit increased allodynia. Glycemia-induced elevation of nuclear factor κB (NFκB) may contribute to increased allodynia.

METHODS

Glycemia during a 3-h ischemia-reperfusion injury was manipulated by: normal feeding; or normal feeding with administration of insulin; dextrose; or insulin/dextrose. In these groups, NFκB was measured in ipsilateral hind paw muscle and spinal dorsal horn by enzyme-linked immunosorbent assay (ELISA), and SN50, an NFκB inhibitor, was administered to determine its differential antiallodynic effects depending on glycemia.

RESULTS

CPIP fed/insulin rats (12.03 ± 4.9 g, N = 6) had less allodynia than fed, fed/insulin/dextrose, and fed/dextrose rats (6.29 ± 3.37 g, N = 7; 4.57 ± 3.03 g, N = 6; 2.95 ± 1.10 g, N = 9), respectively. Compared with fed rats (0.209 ± 0.022 AU, N = 7), NFκB in ipsilateral plantar muscles was significantly lower for fed/insulin rats, and significantly higher for fed/dextrose rats (0.152 ± 0.053 AU, N = 6; 0.240 ± 0.057 AU, N = 7, respectively). Furthermore, NFκB in the dorsal horn of fed, fed/insulin/dextrose, and fed/dextrose rats (0.293 ± 0.049 AU; 0.267 ± 0.037 AU; 0.315 ± 0.015 AU, respectively, N = 6 for each) was significantly higher than in fed/insulin animals (0.267 ± 0.037 AU, N = 6). The antiallodynic SN50 dose-response curves of CPIP rats in the fed/insulin/dextrose, fed/dextrose, and fed conditions exhibited a rightward shift compared with the fed/insulin group. The threshold SN50 dose of CPIP fed/dextrose, fed/insulin/dextrose, and fed rats (328.94 ± 92.4 ng, 77.80 ± 44.50 ng, and 24.89 ± 17.20 ng, respectively) was higher than that for fed/insulin rats (4.06 ± 7.04 ng).

CONCLUSIONS

NFκB was activated in a glycemia-dependent manner in CPIP rats. Hypoglycemic rats were more sensitive to SN50 than rats with higher glycemia. The finding that SN50 reduces mechanical allodynia suggests that NFκB inhibitors might be useful for treating postischemia pain.

Adipose tissue insulin sensitivity and macrophage recruitment: Does PI3K pick the pathway?

In the United States, obesity is a burgeoning health crisis, with over 30% of adults and nearly 20% of children classified as obese. Insulin resistance, a common metabolic complication associated with obesity, significantly increases the risk of developing metabolic diseases such as hypertension, coronary heart disease, stroke, type 2 diabetes, and certain cancers. With the seminal finding that obese adipose tissue harbors cytokine secreting immune cells, obesity-related research over the past decade has focused on understanding adipocyte–macrophage crosstalk and its impact on systemic insulin sensitivity. Indeed, adipose tissue has emerged as a central mediator of obesity- and diet-induced insulin resistance. In this mini-review, we focus on a potential role of adipose tissue phosphoinositide 3-kinase (PI3K) as a point of convergence of cellular signaling pathways that integrates nutrient sensing and inflammatory signaling to regulate tissue insulin sensitivity.

Insulin augments tumor necrosis factor-alpha stimulated expression of vascular cell adhesion molecule-1 in vascular endothelial cells

BACKGROUND

Atherosclerosis is an inflammatory disease that is marked by increased presence of Tumor Necrosis Factor-alpha (TNFα), increased expression of Vascular Cell Adhesion Molecule-1 (VCAM-1), increased presence of serum monocytes and activation of the canonical inflammatory molecule, Nuclear Factor Kappa-B (NFκB). Hyperinsulinemia is a hallmark of insulin resistance and may play a key role in this inflammatory process.

METHODS

Using Western blot analysis, immunocytochemistry, flow cytometry and biochemical inhibitors, we measured changes in VCAM-1 protein expression and NFκB translocation in vascular endothelial cells in the presence of TNFα and/or hyperinsulinemia and in the absence or presence of kinase pathway inhibitors.

RESULTS

We report that hyperinsulinemia augmented TNFα stimulated increases in VCAM-1 protein greater than seen with TNFα alone and decreased the time in which VCAM-1 translocated to the cell surface. We also observed that in the presence of Wortmannin, a biochemical inhibitor of phosphatidylinositol 3-kinase (a hallmark of insulin resistance), VCAM-1 expression was greater in the presence of TNFα plus insulin as compared to that seen with insulin or TNFα alone. Additionally, nuclear import of NFκB occurred sooner in the presence of insulin and TNFα together as compared to each alone, and in the presence of Wortmannin, nuclear import of NFκB was greater than that seen with insulin and TNFα alone.

CONCLUSIONS

hyperinsulinemia and insulin resistance appear to augment the inflammatory effects of TNFα on VCAM-1 expression and NFκB translocation, both of which are markers of inflammation in the vasculature.

Effects of glycemic regulation on chronic postischemia pain

BACKGROUND

Ischemia-reperfusion (I/R) injuries consist of enhanced oxidative and inflammatory responses along with microvascular dysfunction after prolonged ischemia and reperfusion. Because I/R injuries induce chronic postischemia pain (CPIP) in laboratory animals, it is possible that surgical procedures using prolonged ischemia may result in chronic postoperative pain. Glycemic modulation during ischemia and reperfusion could affect pain after I/R injury because glucose triggers oxidative, inflammatory, and thrombotic reactions, whereas insulin has antioxidative, antiinflammatory, and vasodilatory properties.

METHODS

One hundred ten rats underwent a 3-h period of ischemia followed by reperfusion to produce CPIP. Rats with CPIP had previously been divided into six groups with differing glycemic modulation paradigms: normal feeding; fasting; fasting with normal saline administration; fasting with dextrose administration; normal feeding with insulin administration; and normal feeding with insulin and dextrose administration. Blood glucose concentration was assessed during I/R in these separate groups of rats, and these rats were tested for mechanical and cold allodynia over the 21 days afterward (on days 2, 5, 7, 9, 12, and 21 after I/R injury).

RESULTS

I/R injury in rats with normoglycemia or relative hyperglycemia (normal feeding and fasting with dextrose administration groups) led to significant mechanical and cold allodynia; conversely, relative hypoglycemia associated with insulin treatment or fasting (fasting, fasting with normal saline administration, and normal feeding with insulin administration groups) reduced allodynia induced by I/R injury. Importantly, insulin treatment did not reduce allodynia when administered to fed rats given dextrose (normal feeding with dextrose and insulin administration group).

CONCLUSION

Study results suggest that glucose levels at the time of I/R injury significantly modulate postinjury pain thresholds in rats with CPIP. Strict glycemic control during I/R injury significantly reduces CPIP and, conversely, hyperglycemia significantly enhances it, which could have potential clinical applications especially in the surgical field.

Loss of insulin signaling in vascular endothelial cells accelerates atherosclerosis in apolipoprotein E null mice

To determine whether insulin action on endothelial cells promotes or protects against atherosclerosis, we generated apolipoprotein E null mice in which the insulin receptor gene was intact or conditionally deleted in vascular endothelial cells. Insulin sensitivity, glucose tolerance, plasma lipids, and blood pressure were not different between the two groups, but atherosclerotic lesion size was more than 2-fold higher in mice lacking endothelial insulin signaling. Endothelium-dependent vasodilation was impaired and endothelial cell VCAM-1 expression was increased in these animals. Adhesion of mononuclear cells to endothelium in vivo was increased 4-fold compared with controls but reduced to below control values by a VCAM-1-blocking antibody. These results provide definitive evidence that loss of insulin signaling in endothelium, in the absence of competing systemic risk factors, accelerates atherosclerosis. Therefore, improving insulin sensitivity in the endothelium of patients with insulin resistance or type 2 diabetes may prevent cardiovascular complications.

Regulation of oxidative stress by glycaemic control: evidence for an independent inhibitory effect of insulin therapy

AIMS/HYPOTHESIS

We examined whether type of diabetes and/or insulin treatment can modulate the impact of sustained hyperglycaemia and glycaemic variability as activators of oxidative stress.

METHODS

This was an observational study in 139 patients with diabetes, 48 with type 1, 60 with type 2 treated by oral hypoglycaemic agents (OHAs) alone and 31 with type 2 treated with insulin plus OHAs. In addition, two groups of ten patients with type 2 diabetes were investigated either before and after introducing insulin treatment (add-on insulin group) or before and after add-on OHA therapy to metformin (add-on OHA group). Oxidative stress was estimated from 24 h urinary excretion rates of 8-isoprostaglandin F2alpha (8-iso-PGF2alpha). HbA(1c) was assessed and mean amplitude of glycaemic excursions (MAGE) was estimated by continuous monitoring.

RESULTS

The 24 h excretion rate of 8-iso-PGF2alpha (median [range] picomoles per millimole of creatinine) was much higher (p < 0.0001) in type 2 diabetes patients treated with OHAs alone (112 [26-329]) than in the type 1 diabetes group (65 [29-193]) and the type 2 diabetes group treated with insulin (69 [30-198]). It was associated with HbA(1c) (F = 12.9, p = 0.0008) and MAGE (F = 7.7, p = 0.008) in non-insulin-treated, but not in insulin-treated patients. A significant reduction in 24 h excretion rate of 8-iso-PGF2alpha from 126 (47-248) to 62 (35-111] pmol/mmol of creatinine was observed in the add-on insulin group (p = 0.005) but not in the add-on OHA group.

CONCLUSIONS/INTERPRETATION

In type 1 and type 2 diabetes, insulin exerts an inhibitory effect on oxidative stress, a metabolic disorder that is significantly activated by sustained hyperglycaemia and glucose variability in non-insulin-treated type 2 diabetes.

Intensive insulin therapy reduces the urinary intercellular adhesion molecule-1 excretion in patients with Type 2 diabetes mellitus

OBJECTIVE

To observe the change of urinary intercellular adhesion molecule-1 (ICAM-1) excretion in the patients with Type 2 diabetes mellitus (T2DM) compared to normal control group, and to investigate the effect and significance of insulin intensive therapy on the urinary ICAM-1 excretion.

METHOD

We examined the urinary ICAM-1 and creatinine (Cr) of random urine in 20 patients with T2DM and 20 normal subjects using enzyme-linked immunosorbent assay. All diabetics were given intensive insulin therapy for 2 weeks, urinary ICAM- 1 and Cr was examined once again at the end of observation.

RESULTS

Compared with the normal control group, not only the fasting blood glucose (FBG), post-prandial 2-h blood glucose (P2hBG), and glycosylated hemoglobin (HbA1c), but also the urinary ICAM-1 to urinary Cr ratio in patients with T2DM increased significantly (p<0.01). The urinary ICAM-1/urinary Cr ratio of diabetics had a positive correlation with FBG (r=0.51, p<0.01), P2hBG (r=0.496, p<0.01), and HbA1c (r=0.478, p<0.05), respectively. After 2 weeks of intensive insulin therapy in Type 2 diabetics, both the level of blood glucose and the level of urinary ICAM-1/urinary Cr ratio had a remarkable decrease compared with the basal values (p<0.01).

CONCLUSION

Intensive insulin therapy is capable of alleviating the enhanced local inflammation reaction of renal tissue under hyperglycemia state with the reduction of urinary ICAM-1 excretion.

FoxO1 links insulin resistance to proinflammatory cytokine IL-1beta production in macrophages

OBJECTIVE

Macrophages play an important role in the pathogenesis of insulin resistance via the production of proinflammatory cytokines. Our goal is to decipher the molecular linkage between proinflammatory cytokine production and insulin resistance in macrophages.

RESEARCH DESIGN AND METHODS

We determined cytokine profiles in cultured macrophages and identified interleukin (IL)-1β gene as a potential target of FoxO1, a key transcription factor that mediates insulin action on gene expression. We studied the mechanism by which FoxO1 mediates insulin-dependent regulation of IL-1β expression in cultured macrophages and correlated FoxO1 activity in peritoneal macrophages with IL-1β production profiles in mice with low-grade inflammation or insulin resistance.

RESULTS

FoxO1 selectively promoted IL-1β production in cultured macrophages. This effect correlated with the ability of FoxO1 to bind and enhance IL-1β promoter activity. Mutations of the FoxO1 binding site within the IL-1β promoter abolished FoxO1 induction of IL-1β expression. Macrophages from insulin-resistant obese db/db mice or lipopolysaccharide-inflicted mice were associated with increased FoxO1 production, correlating with elevated levels of IL-1β mRNA in macrophages and IL-1 protein in plasma. In nonstimulated macrophages, FoxO1 remained inert with benign effects on IL-1β expression. In response to inflammatory stimuli, FoxO1 activity was augmented because of an impaired ability of insulin to phosphorylate FoxO1 and promote its nuclear exclusion. This effect along with nuclear factor-κB acted to stimulate IL-1β production in activated macrophages.

CONCLUSIONS

FoxO1 signaling through nuclear factor-κB plays an important role in coupling proinflammatory cytokine production to insulin resistance in obesity and diabetes.

Insulin and insulin-like growth factor-I receptors differentially mediate insulin-stimulated adhesion molecule production by endothelial cells

Patients with type 2 diabetes are hyperinsulinemic and insulin resistant and develop premature atherosclerosis. High concentrations of insulin stimulate the production of adhesion molecules by endothelial cells (ECs). ECs express abundant IGF-I receptors as well as insulin receptors. Whether IGF-I receptors contribute to insulin-induced endothelial production of adhesion molecules is unknown. Bovine aortic ECs (BAECs) were incubated with insulin (100 nm) for 24 h. The cellular content of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) was measured, and monocyte adhesion to ECs was quantified. Insulin increased both VCAM-1 (P < 0.001) and ICAM-1 (P < 0.0002) content, which was accompanied by an increased number of monocytes adherent to BAECs (P = 0.0001). Inhibition of either MAPK kinase-1 or p38 MAPK but not phosphatidylinositol 3-kinase abolished insulin-mediated production of adhesion molecules. Insulin receptor small interfering RNA knockdown abolished insulin-stimulated increases of ICAM-1 but not VCAM-1. Conversely, IGF-I receptor blockade with either a neutralizing antibody or specific small interfering RNA eliminated insulin-induced VCAM-1 but not ICAM-1 production. Blockade of signaling via either the insulin or IGF-I receptors decreased monocyte adherence to BAECs (P < 0.01 for each). We conclude that insulin and IGF-I receptors differentially mediate the production of adhesion molecules by ECs and monocyte adhesion onto the vascular endothelium in response to the hyperinsulinemic state. Dual-receptor activation may most effectively contribute to the pathogenesis of atherosclerotic disease in diabetes.

Insulin resistance postburn: underlying mechanisms and current therapeutic strategies

The profound hypermetabolic response to burn injury is associated with insulin resistance and hyperglycemia, significantly contributing to the incidence of morbidity and mortality in this patient population. These responses are present in all trauma, surgical, or critically ill patients, but the severity, length, and magnitude is unique for burn patients. Although advances in therapeutic strategies to attenuate the postburn hypermetabolic response have significantly improved the clinical outcome of these patients during the past years, therapeutic approaches to overcome stress-induced hyperglycemia have remained challenging. Intensive insulin therapy has been shown to significantly reduce morbidity and mortality in critically ill patients. High incidence of hypoglycemic events and difficult blood glucose titrations have led to investigation of alternative strategies, including the use of metformin, a biguanide, or fenofibrate, a peroxisome proliferator-activated receptor (PPAR)-gamma agonist. Nevertheless, weaknesses and potential side affects of these drugs reinforces the need for better understanding of the molecular mechanisms underlying insulin resistance postburn that may lead to novel therapeutic strategies further improving the prognosis of these patients. This review aims to discuss the mechanisms underlying insulin resistance induced hyperglycemia postburn and outlines current therapeutic strategies that are being used to modulate hyperglycemia after thermal trauma.

Acute inhibition of superoxide formation and Rac1 activation by nitric oxide and iloprost in human vascular smooth muscle cells in response to the thromboxane A2 analogue, U46619

BACKGROUND

The over-production of superoxide (O(2)(-)) derived from NADPH oxidase (NOX) plays a central role in cardiovascular diseases. By contrast, nitric oxide (NO) and prostacyclin (PGI(2)) are vasculoprotective. The effect of the NO donor, NONOate and iloprost on O(2)(-) formation, p47(phox) and Rac(1) activation in human vascular smooth muscle cells (hVSMCs) was investigated.

METHODS

hVSMCs were incubated with 10nM thromboxane A(2) analogue, U46619 for 16h, and then with apocynin (a NOX inhibitor), NONOate or iloprost for 1h and O(2)(-) measured spectrophometrically. The role of cyclic AMP and cyclic GMP was examined by co-incubation of drugs with protein kinase (PK) A and G inhibitors listed above. Rac(1) was studied using pull-down assays.

RESULTS

NONOate and iloprost inhibited O(2)(-) formation, acutely, effects blocked by inhibition of PKG and PKA, respectively. Rac(1) and p47(phox) activation and translocation to the plasma membrane was completely inhibited by NONOate and iloprost, effects again reversed by co-incubation with PKG or PKA inhibitors.

CONCLUSIONS

NO and PGI(2) block the acute activity of NOX in hVSMCs via the cGMP-PKG axis (for NO) and by the cAMP-PKA axis (for iloprost) through inhibition of Rac(1) and p47(phox) translocation. These findings have implications in the pathophysiology and treatment of CVD.

Effects of insulin dependence on inflammatory process, thrombotic mechanisms and endothelial function, in patients with type 2 diabetes mellitus and coronary atherosclerosis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is characterized by endothelial dysfunction, increased thrombogenicity and abnormal inflammatory response.

HYPOTHESIS

We hypothesizsed that insulin dependence/exogenous insulin administration may affect thrombotic/inflammatory status and endothelial function in patients with T2DM and coronary artery disease (CAD).

METHODS

Fifty-five patients with T2DM + CAD (26 insulin-treated (INS) and 29 under oral biguanide + sulphonylurea (TABL)) were recruited. Endothelial function was assessed by gauge-strain plethysmography, and serum levels of inflammatory and thrombotic markers were determined by enzyme linked immunosorbent assay.

RESULTS

There was no significant difference in endothelium-dependent dilation (EDD) between the study groups, while EDD was correlated with fasting glucose levels in both INS (r = - 0.776, p = 0.0001) and TABL (r = - 0.702, p = 0.0001). Patients in INS group had higher levels of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), monocyte chemoattractant protein (MCP-1) and vascular cell adhesion molecule (sVCAM-1), compared to TABL. However, TNF-alpha was negatively correlated with protein C (PrtC) only in INS (r = - 0.726, p = 0.01) but not in TABL group (r = - 0.066, p = 0.738). Similarly, sVCAM-1 was correlated with PrtC only among INS patients (r = - 0.451, p = 0.046) but not in TABL (r = 0.069, p = 0.727). In multivariate analysis, insulin dependence was a predictor of IL-6, TNF-alpha, MCP-1 and sVCAM-1 levels independently from the patients' demographic characteristics, the angiographic extend of CAD or the duration of diabetes.

CONCLUSIONS

Insulin treatment in patients with type 2 diabetes mellitus affects the expression of inflammatory cytokines and subsequently modifies the thrombotic mechanisms in patients with coronary atherosclerosis, independently from the duration of diabetes and the extend of coronary artery disease.

Endothelium, inflammation, and diabetes

The endothelium has several diverse functions in maintaining vascular integrity in terms of structure and function. Two key vasodilators, nitric oxide (NO) and prostacyclin, maintain the vascular pathway, inhibit platelet aggregation, and are antithrombotic. More recently, they have been shown to be anti-inflammatory, and thus are potentially antiatherogenic. It has recently been noted that insulin stimulates NO release by the endothelium. Insulin is a vasodilator, has antiplatelet activity, and is anti-inflammatory. Similar anti-inflammatory effects of thiazolidinediones (TZDs), troglitazone and rosiglitazone, suggest that they too may have potential antiatherogenic effects. These effects of insulin and TZDs are important because the two major states of insulin resistance, obesity and type 2 diabetes, are associated with a marked increase in atherosclerosis coronary heart disease, and stroke. These recent observations have extremely momentous implications for the understanding of the pathogenesis of atherosclerosis in insulin-resistant states and for a rational approach to their comprehensive treatment, including the prevention of atherosclerosis and its complications.

Is insulin an endogenous cardioprotector?

Stress hyperglycemia and diabetes mellitus with myocardial infarction are associated with increased risk for in-hospital mortality, congestive heart failure, or cardiogenic shock. Hyperglycemia triggers free radical generation and suppresses endothelial nitric oxide generation, and thus initiates and perpetuates inflammation. Conversely, insulin suppresses production of tumor necrosis factor-alpha and free radicals, enhances endothelial nitric oxide generation, and improves myocardial function. It is proposed that the balance between insulin and plasma glucose levels is critical to recovery and/or complications that occur following acute myocardial infarction and in the critically ill. Adequate attention should be given to maintaining euglycemia (plasma glucose <or= 110 mg/dl) in order to reduce infarct size and improve cardiac function while using a glucose-insulin-potassium cocktail.