Proinflammatory cytokines, markers of cardiovascular risks, oxidative stress, and lipid peroxidation in patients with hyperglycemic crises

Hyperketonemia (ketosis), oxidative stress and type 1 diabetes

The long-term complications of diabetes are the leading causes of morbidity and mortality in the type 1 diabetic population and remain a major public health issue. Hyperglycemia is one of the major risk factors in the development of vascular complications. A growing body of evidence indicates that hyperglycemia leads to increased oxidative stress and monocyte and endothelial cell dysfunction. In addition to hyperglycemia, type 1 diabetic patients frequently experience ketosis (hyperketonemia). The blood concentration of ketone bodies reaches higher than 25mM in diabetics with severe ketosis. Traditionally, clinical practice has considered hypertketonemia to be present only in type 1 diabetic patients. Newer data indicate that diabetic ketoaciosis or hyperketonemia co-exists with hyperglycemia among older type 2 diabetic patients and in African Americans and other minority groups with type 2 diabetes. This review will focus on the role of hyperketonemia in the etiology of oxidative stress in diabetic patients. The data presented here illustrate that the ketone body acetoacetate (AA) can generate superoxide radicals and cause increases in oxidative stress and cellular dysfunction. The data included in this review demonstrate that blood levels of markers of oxidative stress are elevated in hyperketonemic patients compared with those of normoketonemic diabetic patients. Thus, both in vitro and in vivo research indicate that ketosis can generate oxygen radicals and result in excess cellular oxidative stress in type 1 diabetic patients. Elevated oxidative stress levels in ketotic patients can play a significant role in the development of vascular inflammation and contribute to the increased incidence of vascular disease and complications associated with type 1 diabetes.

Palmitic acid-induced activation of human T-lymphocytes and aortic endothelial cells with production of insulin receptors, reactive oxygen species, cytokines, and lipid peroxidation

Diabetic conditions are associated with hyperglycemia and hyperlipidemia, but the role of saturated fatty acids (SFA) vs. unsaturated fatty acids (UFA) in activation of T-lymphocytes and human aortic endothelial cells (HAEC) is not known. We investigated in vitro effects of various concentrations of SFA (palmitate) and UFA (oleic, linoleic, linolenic, and arachidonic) acids in activation of these cells. These cells in presence of palmitate, but not UFA, exhibited time, and concentration-dependent emergence of insulin receptors, GLUT 4 expression, generation of ROS, cytokines, lipid peroxidation, and IRS-1. We conclude that both T-lymphocytes and HAEC share common characteristics in exhibiting activation of these cells to palmitate, but not to UFA, by developing insulin receptors and becoming insulin responsive tissues, a hitherto unknown response to palmitate. We hypothesize that these events may serve as protective defense mechanisms against acute effects of glucotoxicity and lipotoxicity in these cells.

Dysregulated Toll-like receptor expression and signaling in bone marrow-derived macrophages at the onset of diabetes in the non-obese diabetic mouse

The expression, responsiveness and regulation of mouse Toll-like receptors (TLRs) in bone marrow-derived macrophages (BM-Ø) were investigated prior to and following the development of diabetes. Expression of TLR3 and TLR5 was significantly higher in newly diabetic non-obese diabetic (NOD) mice when compared with pre-diabetic and control strains of mice. The TLR3 ligand poly(I)poly(C) triggered up-regulation of its own receptor in NOR and pre-diabetic NOD, but TLR3 was already highly expressed in diabetic NOD mice. Expression levels of TLR3 correlated with poly(I)poly(C)-triggered IFN activity. LPS triggered down-regulation of TLR4 in pre-diabetic NOD, NOR and BALB/c, while levels of TLR4 remained consistently elevated in type 1 diabetic NOD and type 2 diabetic NZL mice. Dysregulation of TLR4 expression in the diabetic state correlated with increased nuclear factor kappa B (NF-kappaB) activation in response to the TLR4 ligand LPS and higher expression of IL-12p40, tumor necrosis factor alpha (TNFalpha), IL-6 and inducible nitric oxide synthase but lowered expression of IL-10. Exposure of bone marrow precursor cells from NOD mice to a hyperglycemic environment during differentiation into macrophages resulted in elevated levels of TLR2 and TLR4 and the cytokine TNFalpha. The results indicate that macrophage precursors are influenced by systemic changes in diabetes favoring altered TLR expression and sensitivity that may influence susceptibility to macrophage-mediated diabetes complications and explain inappropriate responses to infection in diabetes.

Effect of prior hyperglycemia on IL-6 responses to exercise in children with type 1 diabetes

The proinflammatory cytokine interleukin-6 (IL-6) may modulate the onset and progression of complications of diabetes. As this cytokine increases after exercise, and many other exercise responses are altered by prior glycemic fluctuations, we hypothesized that prior hyperglycemia might exacerbate the IL-6 response to exercise. Twenty children with type 1 diabetes (12 boys/8 girls, age 12-15 yr) performed 29 exercise studies (30-min intermittent cycling at approximately 80% peak O2 uptake). Children were divided into four groups based on highest morning glycemic reading [blood glucose (BG) < 150, BG 151-200, BG 201-300, or BG > 300 mg/dl]. All exercise studies were performed in the late morning, after hyperglycemia had been corrected and steady-state conditions (plasma glucose < 120 mg/dl, basal insulin infusion) had been maintained for > or = 90 min. Blood samples for IL-6, growth factors, and counterregulatory hormones were drawn at pre-, end-, and 30 min postexercise time points. At all time points, circulating IL-6 was lowest in BG < 150 and progressively higher in the other three groups. The exercise-induced increment also followed a similar dose-response pattern (BG < 150, 0.6 +/- 0.2 ng/ml; BG 151-200, 1.2 +/- 0.8 ng/ml; BG 201-300, 2.1 +/- 1.1 ng/ml; BG > 300, 3.2 +/- 1.4 ng/ml). Other measured variables (growth hormone, IGF-I, glucagon, epinephrine, cortisol) were not influenced by prior hyperglycemia. Recent prior hyperglycemia markedly influenced baseline and exercise-induced levels of IL-6 in a group of peripubertal children with type 1 diabetes. While exercise is widely encouraged and indeed often considered part of diabetic management, our data underscore the necessity to completely understand all adaptive mechanisms associated with physical activity, particularly in the context of the developing diabetic child.

The endocrine function of adipose tissue: an update

Adipose tissue secretes bioactive peptides, termed 'adipokines', which act locally and distally through autocrine, paracrine and endocrine effects. In obesity, increased production of most adipokines impacts on multiple functions such as appetite and energy balance, immunity, insulin sensitivity, angiogenesis, blood pressure, lipid metabolism and haemostasis, all of which are linked with cardiovascular disease. Enhanced activity of the tumour necrosis factor and interleukin 6 are involved in the development of obesity-related insulin resistance. Angiotensinogen has been implicated in hypertension and plasminogen activating inhibitor-1 (PAI-1) in impaired fibrinolysis. Other adipokines like adiponectin and leptin, at least in physiological concentrations, are insulin sparing as they stimulate beta oxidation of fatty acids in skeletal muscle. The role of resistin is less understood. It is implicated in insulin resistance in rats, but probably not in humans. Reducing adipose tissue mass, through weight loss in association with exercise, can lower TNF-alpha and IL-6 levels and increase adiponectin concentrations, whereas drugs such as thiazolinediones increase endogenous adiponectin production. In-depth understanding of the pathophysiology and molecular actions of adipokines may, in the coming years, lead to effective therapeutic strategies designed to protect against atherosclerosis in obese patients.

De novo emergence of insulin-stimulated glucose uptake in human aortic endothelial cells incubated with high glucose

Elevated glucose concentrations have profound effects on cell function. We hypothesized that incubation of human aortic endothelial cells (HAEC) with high glucose increases insulin signaling and develops the appearance of insulin-stimulated glucose uptake by the cells. Compared with 5 mM glucose, incubation of HAEC with 30 mM glucose for up to 48 h increased in a time-dependent manner expression of insulin receptor, insulin receptor substrate (IRS)-1, IRS-2, and GLUT1 proteins. High glucose also increased the specific binding of (125)I-labeled insulin in HAEC accompanied by accelerated production of interleukin (IL)-6 and IL-8. Short-term stimulation by 50 microU/ml insulin did not activate [(14)C]glucose uptake by HAEC incubated in 5 mM glucose. However, an addition of insulin to high glucose-exposed endothelial cells led to a significant increase in [(14)C]glucose uptake in a glucose concentration- and time-dependent fashion, reaching a plateau at 48 h of incubation. Furthermore, incubation of HAEC with 30 mM glucose resulted in a new insulin-stimulated extracellular signal-regulated kinase-1/2 mitogen-activated protein kinase phosphorylation and increased lipid peroxidation and production of reactive oxygen species. These studies show for the first time that high glucose increases expression of insulin receptors and downstream elements of the insulin-signaling pathway and transforms "insulin-resistant" aortic endothelial cells into "insulin-sensitive" tissue regarding glucose uptake.

Pediatric diabetic ketoacidosis and hyperglycemic hyperosmolar state

Diabetic ketoacidosis is an important complication of diabetes in children and is the most frequent diabetes-related cause of death in childhood. The pathophysiology of this condition can be viewed as an exaggeration of the normal physiologic mechanisms responsible for maintaining an adequate fuel supply to the brain and other tissues during periods of fasting and physiologic stress. The optimal therapy has been a subject of controversy, particularly because the most frequent serious complication of diabetic ketoacidosis-cerebral edema-and the relationship of this complication to treatment are incompletely understood. In this article, the author reviews the pathophysiology of diabetic ketoacidosis and its complications and presents an evidence-based approach to the management of this condition.

Influence of the DASH diet and other low-fat, high-carbohydrate diets on blood pressure

The Dietary Approaches to Stop Hypertension (DASH) and DASH-sodium trials were controlled feeding dietary trials that lowered blood pressure in the absence of weight loss. The beneficial aspect of DASH appears to be the low saturated fat content (< 7%). Sodium restriction added additional blood pressure lowering to the low saturated fat DASH diet. Sodium restriction was more effective with increasing age and more effective than increasing fruit and vegetable content. When achievement of sodium restriction, exercise, and weight loss goals were reached in the outpatient setting with subjects making their own food choices (as in the PREMIER study), adding the DASH diet with an average fruit and vegetable intake of 7.8 servings daily had no additional benefit in those younger than 50 years of age or in ethnic/gender subgroups, but did have a benefit for the total group older than age 50 years. Because many hypertensive subjects are overweight, hypocaloric versions of DASH geared toward weight loss are appropriate. Mechanisms for dietary beneficial effects are related to inflammation and insulin sensitivity.

Hyperglycemia-induced activation of human T-lymphocytes with de novo emergence of insulin receptors and generation of reactive oxygen species

Upon activation by phytohemagglutine (PHA), T-lymphocytes (T-cells) express receptors for growth factors, insulin, IGF-1 and IL2 and become insulin sensitive. Diabetic ketoacidosis (DKA) is associated with in vivo emergence of these growth factor receptors without incubation with PHA. As DKA consists of multiple metabolic alterations, in addition to hyperglycemia, we investigated the in vitro effect of different concentrations of glucose (5, 15, and 30 mM) in isolated CD4 of human T-cells at various time intervals (0, 24, 48, and 72 h). Hyperglycemia, but not euglycemia, resulted in de novo emergence of growth factor receptors in a dose- and time-dependent fashion. The activation was also associated with incremental changes in GLUT 4, IRS-1, proinflammatory cytokines, and oxidative stress components. We propose that activation of T-cells with development of insulin receptors in hyperglycemic conditions may serve as a mechanism for control of glucose entry into these cells, thus, protecting them against glucose toxicity.

Insulin infusion in acute illness

The discovery of the antiinflammatory effect of insulin and the proinflammatory effect of glucose has not only provided novel insight into the mechanisms underlying several disease states but has also provided a rationale for the treatment of hyperglycemia in several acute clinical conditions. Van den Berghe et al. previously showed the benefits of intensive glycemic control with insulin in patients admitted to intensive care units. In this issue of the JCI, the same group of investigators now demonstrates that infusion of insulin to restore euglycemia in these patients results in a marked reduction in inflammatory indices such as adhesion molecules, hepatic iNOS, and plasma NO metabolites. The reduction in the mediators of inflammation may thus be responsible for the impressive improvement in clinical outcomes following insulin therapy, and the results suggest a new paradigm in which glucose and insulin are related not only through their metabolic actions but also through their opposite effects on inflammatory mechanisms.

Insulin and its analogue glargine do not affect viability and proliferation of human coronary artery endothelial and smooth muscle cells

AIMS/HYPOTHESIS

Present guidelines for the treatment of type 2 diabetes recommend HbA1c values of less than 7%. As beta cell function worsens during progress of the disease, insulin therapy is often necessary to achieve this ambitious goal. However, due to peripheral insulin resistance, many patients need rather high insulin dosages. In the light of the extremely high cardiovascular risk of diabetic patients, it is important to determine whether high concentrations of insulin or its frequently used analogues are harmful to the cardiovascular system. We therefore investigated the modulatory effects of regular human insulin and its analogue glargine on proliferation and apoptosis of human coronary artery endothelial cells (HCAECs) and human coronary artery smooth muscle cells (HCASMCs).

METHODS

Cells were treated with regular human insulin or insulin glargine. Proliferation was determined by [3H]thymidine incorporation and by flow cytometric analysis of Ki-67 expression. Apoptosis was assessed by flow cytometry (cell cycle analysis and annexin V staining) and determination of caspase-3 activity.

RESULTS

HCAECs and HCASMCs treated with regular human insulin or insulin glargine did not show significant increases in DNA synthesis or Ki-67 expression. Administration of regular human insulin or insulin glargine did not modulate the extent of apoptotic events. No influence of insulin on lipoapoptotic vascular cell death could be detected.

CONCLUSIONS/INTERPRETATION

Taken together, neither regular human insulin nor insulin glargine influences growth and apoptosis of human coronary artery cells in vitro. Our data do not suggest that regular human insulin or insulin glargine promote atherosclerosis through mechanisms affecting the cellularity of human coronary arteries.

Inflammatory response during hyperglycemia and hyperinsulinemia in a porcine endotoxemic model: the contribution of essential organs

BACKGROUND

During euglycemia acute hyperinsulinemia diminishes the cytokine response to endotoxin [Lipopolysaccharide (LPS)] exposure. In this study we elucidated whether acute hyperglycemia and hyperinsulinemia modify the cytokine content in several organs during LPS challenge in a porcine model.

METHODS

Pigs (35-40 kg) were randomized to either normoglycemia (group 1, n = 8) or hyperglycemia and hyperinsulinemia (group 2, n = 8), anesthetized and mechanically ventilated. Both groups received a 180-min intravenous infusion of LPS (total 10 microg kg(-1)). Groups 1 and 2 were clamped at plasma glucose concentrations of 5 mM and 15 mM, respectively. Group 1 maintained a baseline insulin level while the hyperglycemic group exhibited increased insulin levels.

RESULTS

Circulating cytokines, cytokine mRNA and cytokine protein content were examined in the heart, liver, kidneys, lungs, spleen, adipose and muscle tissue. After LPS exposure, in both groups vast and equal plasma cytokines were elicited by approximately 70-5000-fold. A 10-fold higher level of IL-10, IL-6 and TNF-alpha protein was found in kidney tissue compared to the other organs together with a 3-10-fold increase of TNF-alpha in adipose tissue. However, cytokine mRNAs as well as organ function were without statistical difference between the groups.

CONCLUSION

Endotoxemia elicited a pronounced cytokine response in both plasma and at organ level. The kidneys and adipose tissue showed the highest cytokine protein content. Acute hyperglycemia apparently counteracts the well-established anti-inflammatory effects of insulin on the inflammatory response in a LPS challenged porcine model. Whether the observation can be extrapolated to more long-term stress-exposure remains to be clarified.

Role of oxidative stress in diabetic nephropathy

Accumulating research suggests that oxidative stress is a significant contributor to the pathogenesis of diabetic nephropathy. The normal kidney generates a substantial amount of oxidative stress because of its high metabolic activity that is balanced by an extensive antioxidant system. However, in pathologic states such as hyperglycemia, nitroso-oxidant balance shifts toward a pro-oxidant state that accelerates tissue and vascular injury. This oxidative damage progresses concomitant with worsening glucose metabolism, vascular dysfunction, and kidney disease. Accordingly, strategies to reduce oxidative stress in diabetes mellitus may exert favorable effects on the progression of diabetic nephropathy.

Transcriptome and proteome expression in activated human CD4 and CD8 T-lymphocytes

T-lymphocytes (T-cells) are unique in that unlike monocytes, they have no insulin receptors, and are insulin insensitive, but upon activation with antigens develop insulin, IGF-1, and IL-2 receptors, and become insulin sensitive tissues. In vivo activation of these cells has now been demonstrated in patients with diabetic ketoacidosis. We analyzed the genomics and proteomics of activated and non-activated CD4+ and CD8+ T-cells of normal subjects using Affymetrix microarray gene chips and proteomes by SELDI-TOF mass spectrometry analysis. Genes for IL-2, insulin, and IGF-1 receptors were increased at least 2-fold in activated vs non-activated T-cells. Using an expression array containing the entire human genome of 39,500 genes, we evaluated approximately 27,000 genes relevant in physiologic and cellular ontologies. Of these, approximately 10,500 genes were increased in activated cells, compared to about 7,000, which were decreased, and approximately 9500, which were unchanged. Among activated ontologies were signal transduction pathways such as IRS-1, IRS-2, Akt, and glycolytic pathways. To our knowledge this is the first report of an hitherto unreported event. Possible implications of these processes are discussed in the light of their physiological significance.