Suppression of nuclear factor-kappaB and stimulation of inhibitor kappaB by troglitazone: evidence for an anti-inflammatory effect and a potential antiatherosclerotic effect in the obese

Insulin Resistance and Atherosclerosis: Implications for Insulin-Sensitizing Agents

Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.

The role of oxidant stress and gender in the erythrocyte arginine metabolism and ammonia management in patients with type 2 diabetes

OBJECTIVES

To study the differences in the levels of nitrogen metabolites, such as ammonia and nitric oxide and the correlations existing among them in both red blood cells (RBCs) and serum, as well as the possible differences by gender in healthy subjects and patients with type 2 Diabetes Mellitus (DM).

DESIGN AND METHODS

This cross-sectional study included 80 patients diagnosed with type 2 DM (40 female and 40 male patients) and their corresponding controls paired by gender (40 female and 40 male). We separated serum and RBC and determined metabolites mainly through colorimetric and spectrophotometric assays. We evaluated changes in the levels of the main catabolic by-products of blood nitrogen metabolism, nitric oxide (NO), and malondialdehyde (MDA).

RESULTS

Healthy female and male controls showed a differential distribution of blood metabolites involved in NO metabolism and arginine metabolism for the ornithine and urea formation. Patients with DM had increased ammonia, citrulline, urea, uric acid, and ornithine, mainly in the RBCs, whereas the level of arginine was significantly lower in men with type 2 DM. These findings were associated with hyperglycemia, glycosylated hemoglobin (Hb A1C), and levels of RBC's MDA. Furthermore, most of the DM-induced alterations in nitrogen-related metabolites appear to be associated with a difference in the RBC capacity for the release of these metabolites, thereby causing an abrogation of the gender-related differential management of nitrogen metabolites in healthy subjects.

CONCLUSIONS

We found evidence of a putative role of RBC as an extra-hepatic mechanism for controlling serum levels of nitrogen-related metabolites, which differs according to gender in healthy subjects. Type 2 DM promotes higher ammonia, citrulline, and MDA blood levels, which culminate in a loss of the differential management of nitrogen-related metabolites seen in healthy women and men.

Effects of astaxanthin supplementation in healthy and obese dogs

Background

Since astaxanthin (ASX) has potent anti-oxidative effects with inhibitory action of lipid peroxidation and singlet oxygen quenching activity, it is widely used as a functional food for keeping good health in human. Obesity is a risk factor for various metabolic disorders. It is characterized by low-grade chronic inflammation based on oxidative stress by excessively produced ROS. From the point of preventive medicine, natural compounds have been proposed as potential therapeutic agents in the prevention of metabolic disorder in companion animals. The purpose of this study is to evaluate the effects of ASX supplementation in healthy and obese dogs.

Materials and methods

Ten healthy beagle dogs and 5 clinically obese dogs were used in this study. The healthy beagle dogs were randomly divided into 2 groups as follows: control and test groups. The test group dogs received ASX supplementation mixed with the food for 6 weeks. Five clinically obese dogs received ASX supplementation for 8 weeks. Metabolites, hormones and enzymes were measured before and after ASX supplementation.

Results

In the healthy dog groups, after 6 weeks, plasma triglyceride (TG) and malondialdehyde concentrations and lactate dehydrogenase (LDH) values significantly decreased in the test group. There was no significant difference in the control group. In clinically obese dogs, plasma TG concentration decreased after 8 weeks of ASX supplementation. Plasma alanine aminotransferase and LDH values clearly decreased in all 5 dogs and 4 dogs out of 5 dogs, respectively.

Conclusion

ASX supplementation (0.3 mg/kg body weight/day) for 6 weeks in healthy dogs and 8 weeks in obese dogs induced the elevation of antioxidant function and of liver function by ameliorating lipid metabolism.

Ginseng oligopeptides protect against irradiation-induced immune dysfunction and intestinal injury

Intestinal injury and immune dysfunction are commonly encountered after irradiation therapy. While the curative abilities of ginseng root have been reported in prior studies, there is little known regarding its role in immunoregulation of intestinal repairability in cancer patients treated with irradiation. Our current study aims to closely examine the protective effects of ginseng-derived small molecule oligopeptides (Panax ginseng C. A. Mey.) (GOP) against irradiation-induced immune dysfunction and subsequent intestinal injury, using in vitro and in vivo models. Expectedly, irradiation treatment resulted in increased intestinal permeability along with mucosal injury in both Caco-2 cells and mice, probably due to disruption of the intestinal epithelial barrier, leading to high plasma lipopolysaccharide (LPS) and pro-inflammatory cytokines levels. However, when the cells were treated with GOP, this led to diminished concentration of plasma LPS and cytokines (IL-1 and TNF-α), suggesting its dampening effect on inflammatory and oxidative stress, and potential role in restoring normal baseline intestinal permeability. Moreover, the Caco-2 cells treated with GOP showed high trans-epithelial electrical resistance (TEER) and low FITC-dextran paracellular permeability when compared to the control group. This could be explained by the higher levels of tight junction proteins (ZO-1 and Occludin) expression along with reduced expression of the apoptosis-related proteins (Bax and Caspase-3) noticed in the GOP-treated cells, highlighting its role in preserving intestinal permeability, through prevention of their degradation while maintaining normal levels of expression. Further confirmatory in vivo data showed that GOP-treated mice exhibited high concentrations of lymphocytes (CD3+, CD4+, CD8+) in the intestine, to rescue the irradiation-induced damage and restore baseline intestinal integrity. Therefore, we propose that GOP can be used as an adjuvant therapy to attenuate irradiation-induced immune dysfunction and intestinal injury in cancer patients.

PPAR-γ receptor agonists-a review of their role in diabetic management in Trinidad and Tobago

The PPAR-γ receptor agonists, as a relatively new and perhaps still not very widely used class of antidiabetic agent in the Caribbean and particularly the Trinidadian context, possess pharmacologic properties that certainly have been shown to have impact on many of the inflammatory, metabolic, biochemical and structural macrovascular aberrations that occur in the type 2 diabetic. Activation of PPAR(gamma) nuclear receptors regulates the transcription of insulin-responsive genes involved in the control of glucose production, transport, and utilization. PPAR(gamma)-responsive genes also participate in the regulation of fatty acid metabolism, an important contributory pathogenic factor in this subset of patients. The unique mode of action of this class of therapeutic agent addresses a range of anomalies occurring at the cellular and sub-cellular level that are injurious to the diabetic. My aim in addressing the issue of the potential impact of PPAR-γ receptor agonists on cardiovascular disease (CVD) morbidity and mortality in the diabetic, is first, to seek to enhance both an awareness of, and greater familiarity among our own physicians, with this class of drug, and secondly, to effect a timely review of the recent literature as it relates to the tremendous possibilities for the potential clinical gains that might accrue from their use, in so far as this may serve to ameliorate the ravages of the CVD disease that all too tragically attends the type 2 diabetic, and more specifically those with the insulin resistance syndrome. (Mol Cell Biochem 263: 189-210, 2004).

Serum levels of monocyte chemoattractant protein-1 and all-cause and cardiovascular mortality among patients with coronary artery disease

Background

Monocyte chemoattractant protein-1 (MCP-1) is an important chemokine at multiple phases of atherosclerosis in animals, but human studies are few and inconsistent. The aim of this study is to investigate the association of serum MCP-1with all-cause and cardiovascular disease (CVD) mortality among coronary artery disease (CAD) patients and determine whether this biomarker can add secondary prognostic value to standard risk predictors.

Methods

MCP-1 was measured at baseline in 1411 CAD patients who were 40–85 years of age. Cox proportional hazards regression models were used to estimate the association of MCP-1 levels with death risk.

Results

During a median follow-up of 3.3 years, 117 deaths were recorded, 88 of which were due to CVD. The multivariable-adjusted hazard ratios across tertiles of MCP-1 were 1.51 (95% confidence intervals [CI] 0.89–2.58), 1.00, and 2.11 (95% CI 1.31–3.40) for all-cause mortality, and 1.50 (95% CI 0.80–2.81), 1.00, and 2.21 (95% CI 1.27–3.87) for CVD mortality. The addition of serum MCP-1 to the fully adjusted model increased the C-index by 0.009 (p<0.0001) for all-cause mortality and 0.008 (p<0.0001) for CVD mortality and significantly improved the predictive ability by 12.1% (P = 0.006) on all-cause mortality and 12.6% (P = 0.003) on CVD mortality using the net reclassification improvement method.

Conclusions

Both lower and higher MCP-1 levels are associated with an increased risk of all-cause and CVD mortality among CAD patients. More research is needed to confirm its clinical relevance.

Identification of sucrose non-fermenting-related kinase (SNRK) as a suppressor of adipocyte inflammation

In this study, the role of sucrose non-fermenting-related kinase (SNRK) in white adipocyte biology was investigated. SNRK is abundantly expressed in adipose tissue, and the expression level is decreased in obese mice. SNRK expression is repressed by inflammatory signals but increased by insulin sensitizer in cultured adipocytes. In vivo, adipose tissue SNRK expression can be decreased by lipid injection but enhanced by macrophage ablation. Knocking down SNRK in cultured adipocytes activates both JNK and IKKβ pathways as well as promotes lipolysis. Insulin-stimulated Akt phosphorylation and glucose uptake are impaired in SNRK knockdown adipocytes. Phosphoproteomic analysis with SNRK knockdown adipocytes revealed significantly decreased phosphorylation of 49 proteins by 25% or more, which are involved in various aspects of adipocyte function with a clear indication of attenuated mTORC1 signaling. Phosphorylation of 43 proteins is significantly increased by onefold or higher, among which several proteins are known to be involved in inflammatory pathways. The inflammatory responses in SNRK knockdown adipocytes can be partially attributable to defective mTORC1 signaling, since rapamycin treatment activates IKKβ and induces lipolysis in adipocytes. In summary, SNRK may act as a suppressor of adipocyte inflammation and its presence is necessary for maintaining normal adipocyte function.

Adipose tissue macrophages in the development of obesity-induced inflammation, insulin resistance and type 2 diabetes

It has been increasingly accepted that chronic subacute inflammation plays an important role in the development of insulin resistance and type 2 diabetes in animals and humans. Particularly supporting this is that suppression of systemic inflammation in type 2 diabetes improves glycemic control; this also points to a new potential therapeutic target for the treatment of type 2 diabetes. Recent studies strongly suggest that obesity-induced inflammation is mainly mediated by tissue resident immune cells, with particular attention being focused on adipose tissue macrophages (ATMs). This review delineates the current progress made in understanding obesity-induced inflammation and the roles ATMs play in this process.

Human adipose dynamics and metabolic health

The two types of adipose tissue in humans, white and brown, have distinct developmental origins and functions. Human white adipose tissue plays a pivotal role in maintaining whole-body energy homeostasis by storing triglycerides when energy is in surplus, releasing free fatty acids as a fuel during energy shortage, and secreting adipokines that are important for regulating lipid and glucose metabolism. The size of white adipose mass needs to be kept at a proper set point. Dramatic expansion of white fat mass causes obesity—now become a global epidemic disease—and increases the risk for the development of many life-threatening diseases. The absence of white adipose tissue or abnormal white adipose tissue redistribution leads to lipodystrophy, a condition often associated with metabolic disorders. Brown adipose tissue is a thermogenic organ whose mass is inversely correlated with body mass index and age. Therapeutic approaches targeting adipose tissue have been proven to be effective in improving obesity-related metabolic disorders, and promising new therapies could be developed in the near future.

Monocyte Chemoattractant Protein 1 (MCP-1) in obesity and diabetes

Monocyte Chemoattractant Protein-1 (MCP-1) is the first discovered and most extensively studied CC chemokine, and the amount of studies on its role in the etiologies of obesity- and diabetes-related diseases have increased exponentially during the past two decades. This review attempted to provide a panoramic perspective of the history, regulatory mechanisms, functions, and therapeutic strategies of this chemokine. The highlights of this review include the roles of MCP-1 in the development of obesity, diabetes, cardiovascular diseases, insulitis, diabetic nephropathy, and diabetic retinopathy. Therapies that specifically or non-specifically inhibit MCP-1 overproduction have been summarized.

The impact of diabetes on the pathogenesis of sepsis

Diabetes is associated with an increased susceptibility to infection and sepsis. Conflicting data exist on whether the mortality of patients with sepsis is influenced by the presence of diabetes, fuelling the ongoing debate on the benefit of tight glucose regulation in patients with sepsis. The main reason for which diabetes predisposes to infection appears to be abnormalities of the host response, particularly in neutrophil chemotaxis, adhesion and intracellular killing, defects that have been attributed to the effect of hyperglycaemia. There is also evidence for defects in humoral immunity, and this may play a larger role than previously recognised. We review the literature on the immune response in diabetes and its potential contribution to the pathogenesis of sepsis. In addition, the effect of diabetes treatment on the immune response is discussed, with specific reference to insulin, metformin, sulphonylureas and thiazolidinediones.

Assessment of different bariatric surgeries in the treatment of obesity and insulin resistance in mice

OBJECTIVE

To assess the effects of different bariatric surgical procedures on the treatment of obesity and insulin resistance in high fat diet-induced obese (DIO) mice.

BACKGROUND

Bariatric surgery is currently considered the most effective treatment for morbid obesity and its comorbidities; however, a systematic study of their mechanisms is still lacking.

METHODS

We developed bariatric surgery models, including gastric banding, sleeve gastrectomy, Roux-en-Y gastric bypass (RYGB), modified RYGB (mRYGB) and biliopancreatic diversion (BPD), in DIO mice. Body weight, body fat and lean mass, liver steatosis, glucose tolerance and pancreatic beta cell function were examined.

RESULTS

All bariatric surgeries resulted in significant weight loss, reduced body fat and improved glucose tolerance in the short term (4 weeks), compared with mice with sham surgery. Of the bariatric surgery models, sleeve gastrectomy and mRYGB had higher success rates and lower mortalities and represent reliable restrictive and gastrointestinal (GI) bypass mouse bariatric surgery models, respectively. In the long term, the GI bypass procedure produced more profound weight loss, significant improvement of glucose tolerance and liver steatosis than the restrictive procedure. DIO mice had increased insulin promoter activity, suggesting overactivation of pancreatic beta cells, which was regulated by the mRYGB procedure. Compared with the restrictive procedure, the GI bypass procedure showed more severe symptoms of malnutrition following bariatric surgery.

DISCUSSIONS

Both restrictive and GI bypass procedures provide positive effects on weight loss, fat composition, liver steatosis and glucose tolerance; however, in the long term, the GI bypass shows better results than restrictive procedures.

Downregulation of the proinflammatory state of circulating mononuclear cells by short-term treatment with pioglitazone in patients with type 2 diabetes mellitus and coronary artery disease

Background. This study was performed to investigate the influence of a short-term treatment with pioglitazone versus placebo on inflammatory activation of mononuclear cells (mRNA expression/protein secretion of inflammatory markers). Methods and Results. Sixty-three patients with well-controlled type 2 diabetes (52 males, 11 females, age (Mean ± SD): 66 ± 7 yrs, disease duration: 6.6 ± 9.6 yrs, HbA1c: 6.7 ± 0.6%) were randomized to additional 45 mg of pioglitazone or placebo to their existing metformin and sulfonylurea therpay for four weeks in a double-blind study design. Protein risk marker levels (hsCRP, MMP-9, MCP-1, etc.) and the expression of NFκB subunits and NFκB-modulated cytokines from isolated peripheral monocyte/macrophages were determined at baseline and endpoint. There were no changes in HbA1c, but significant biomarker improvements were seen with pioglitazone only. The mRNA marker expression was downregulated by pioglitazone and further up-regulated with placebo (e.g., P105 pioglitazone: −19%/placebo: +6%, RelA: −20%/+2%, MMP−9: −36%/+9%, TNFα: −10%/+14%, P < 0.05 between groups in all cases). Conclusions. Pioglitazone very rapidly down-regulated the activated state of peripheral monocytes/macrophages as assessed by mRNA expression of NFκB and NFκB-modulated cytokines and decreased plasma levels of cardiovascular risk marker proteins independent of glycemic control.

Inhibitory effect of rosiglitazone on the acid-induced intracellular generation of hydrogen peroxide in cultured feline esophageal epithelial cells

Peroxisome proliferator-activated receptor-gamma (PPARγ) agonists have been reported to enhance antioxidant defenses by increasing levels of catalase and copper-zinc superoxide dismutase (Cu/Zn SOD) in oligodendrocyte progenitor cells. In this study, we investigated the effects of the PPARγ agonist, rosiglitazone, on hydrogen peroxide (H(2)O(2)) generation by acidified medium at pH 5.5 (AM5.5), which is in the pH range of duodenogastric refluxates, in primary cultured feline esophageal epithelial cells (EEC). Successful isolation of EEC was identified by immunocytochemistry. AM5.5- and rosiglitazone-induced cell viabilities were determined using 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide assays. The NAD(P)H oxidase activity was measured, and expression of catalase or SOD protein by AM5.5 in the absence and presence of rosiglitazone was assessed using western blotting analysis. PPARγ protein and mRNA were constitutively expressed in EEC. In the incubation with rosiglitazone alone, cell viability was shown more than 90% at 0-10 μM for 72 h. After exposure to AM5.5 for 8 h, intracellular H(2)O(2) was significantly generated. Treatment with rosiglitazone prior to and during exposure to AM5.5 inhibited the H(2)O(2) generation whereas the specific PPARγ antagonist GW9662 offsets the inhibitory action of rosiglitazone. H(2)O(2) generation was also prevented by a nonspecific ROS scavenger N-acetylcysteine or an inhibitor of NADPH oxidase diphenyleneiodonium. The enhanced AM5.5-induced NAD(P)H oxidase activity was not suppressed by rosiglitazone. Instead, the pretreatment of rosiglitazone enhanced the protein expression of catalase, Cu/Zn SOD, and Mn SOD, which are endogenous antioxidative enzymes. These findings indicate that rosiglitazone inhibits AM5.5-induced intracellular H(2)O(2) production, which occurs via NAD(P)H oxidase activation, by using a PPARγ-dependent pathway, and that the underlying mechanism involves an increase in the expression of catalase and SOD proteins.

Use of salsalate to target inflammation in the treatment of insulin resistance and type 2 diabetes

OBJECTIVES

Chronic subacute inflammation is implicated in the pathogenesis of insulin resistance and type 2 diabetes. Salicylates were shown years ago to lower glucose and more recently to inhibit NF-kappaB activity. Salsalate, a prodrug form of salicylate, has seen extensive clinical use and has a favorable safety profile. We studied the efficacy of salsalate in reducing glycemia and insulin resistance and potential mechanisms of action to validate NF-kappaB as a potential pharmacologic target in diabetes.

METHODS AND RESULTS

In open label studies, both high (4.5 g/d) and standard (3.0 g/d) doses of salsalate reduced fasting and postchallenge glucose levels after 2 weeks of treatment. Salsalate increased glucose utilization during euglycemic hyperinsulinemic clamps, by approximately 50% and 15% at the high and standard doses, respectively, and insulin clearance was decreased. Dose-limiting tinnitus occurred only at the higher dose. In a third, double-masked, placebo-controlled trial, 1 month of salsalate at maximum tolerable dose (no tinnitus) improved fasting and postchallenge glucose levels. Circulating free fatty acids were reduced and adiponectin increased in all treated subjects.

CONCLUSIONS

These data demonstrate that salsalate improves in vivo glucose and lipid homeostasis, and support targeting of inflammation and NF-kappaB as a therapeutic approach in type 2 diabetes.

Targeting inflammation-induced obesity and metabolic diseases by curcumin and other nutraceuticals

Extensive research within the past two decades has revealed that obesity, a major risk factor for type 2 diabetes, atherosclerosis, cancer, and other chronic diseases, is a proinflammatory disease. Several spices have been shown to exhibit activity against obesity through antioxidant and anti-inflammatory mechanisms. Among them, curcumin, a yellow pigment derived from the spice turmeric (an essential component of curry powder), has been investigated most extensively as a treatment for obesity and obesity-related metabolic diseases. Curcumin directly interacts with adipocytes, pancreatic cells, hepatic stellate cells, macrophages, and muscle cells. There, it suppresses the proinflammatory transcription factors nuclear factor-kappa B, signal transducer and activators of transcription-3, and Wnt/beta-catenin, and it activates peroxisome proliferator-activated receptor-gamma and Nrf2 cell-signaling pathways, thus leading to the downregulation of adipokines, including tumor necrosis factor, interleukin-6, resistin, leptin, and monocyte chemotactic protein-1, and the upregulation of adiponectin and other gene products. These curcumin-induced alterations reverse insulin resistance, hyperglycemia, hyperlipidemia, and other symptoms linked to obesity. Other structurally homologous nutraceuticals, derived from red chili, cinnamon, cloves, black pepper, and ginger, also exhibit effects against obesity and insulin resistance.

An antiinflammatory and reactive oxygen species suppressive effects of an extract of Polygonum cuspidatum containing resveratrol

BACKGROUND

Resveratrol have been shown to exert an antiinflammatory and antiaging effects in vitro and in animal models.

OBJECTIVE

The objective of the study was to investigate the effect of a Polygonum cuspidatum extract (PCE) containing resveratrol on oxidative and inflammatory stress in normal subjects.

RESEARCH DESIGN AND METHODS

Two groups (10 each) of normal-weight healthy subjects were randomized to placebo or PCE containing 40 mg resveratrol daily for 6 wk. Fasting blood samples were obtained prior to and after treatment at 1, 3, and 6 wk. Mononuclear cells were prepared for reactive oxygen species generation, RNA isolation, nuclear extract, and total cell homogenate preparation. Indices of oxidative and inflammatory stress, suppressor of cytokine signaling-3, phosphotyrosine phosphatase-1B, jun-N-terminal kinase-1, and inhibitor of kappaB-kinase-beta were measured by RT-PCR and Western blotting.

RESULTS

The extract induced a significant reduction in reactive oxygen species generation, the expression of p47(phox), intranuclear nuclear factor-kappaB binding, and the expression of jun-N-terminal kinase-1, inhibitor of kappaB-kinase-beta, phosphotyrosine phosphatase-1B, and suppressor of cytokine signaling-3 in mononuclear cells when compared with the baseline and the placebo. PCE intake also suppressed plasma concentrations of TNF-alpha, IL-6, and C-reactive protein. There was no change in these indices in the control group given placebo.

CONCLUSIONS

The PCE-containing resveratrol has a comprehensive suppressive effect on oxidative and inflammatory stress.

Insulin resistance, lipotoxicity, type 2 diabetes and atherosclerosis: the missing links. The Claude Bernard Lecture 2009

Insulin resistance is a hallmark of type 2 diabetes mellitus and is associated with a metabolic and cardiovascular cluster of disorders (dyslipidaemia, hypertension, obesity [especially visceral], glucose intolerance, endothelial dysfunction), each of which is an independent risk factor for cardiovascular disease (CVD). Multiple prospective studies have documented an association between insulin resistance and accelerated CVD in patients with type 2 diabetes, as well as in non-diabetic individuals. The molecular causes of insulin resistance, i.e. impaired insulin signalling through the phosphoinositol-3 kinase pathway with intact signalling through the mitogen-activated protein kinase pathway, are responsible for the impairment in insulin-stimulated glucose metabolism and contribute to the accelerated rate of CVD in type 2 diabetes patients. The current epidemic of diabetes is being driven by the obesity epidemic, which represents a state of tissue fat overload. Accumulation of toxic lipid metabolites (fatty acyl CoA, diacylglycerol, ceramide) in muscle, liver, adipocytes, beta cells and arterial tissues contributes to insulin resistance, beta cell dysfunction and accelerated atherosclerosis, respectively, in type 2 diabetes. Treatment with thiazolidinediones mobilises fat out of tissues, leading to enhanced insulin sensitivity, improved beta cell function and decreased atherogenesis. Insulin resistance and lipotoxicity represent the missing links (beyond the classical cardiovascular risk factors) that help explain the accelerated rate of CVD in type 2 diabetic patients.

Lipid-induced insulin resistance is prevented in lean and obese myotubes by AICAR treatment

The molecular mechanisms of obesity-associated insulin resistance are becoming increasingly clear, and the effects of various lipid molecules, such as diacylglycerol and ceramide, on the insulin signal are being actively explored. To better understand the divergent response to lipid exposure between lean and obese, we incubated primary human muscle cells from lean [body mass index (BMI) <25 kg/m(2)] and morbidly obese (BMI >40 kg/m(2)) subjects with the saturated fatty acid palmitate. Additionally, given that AMPK-activating drugs are widely prescribed for their insulin-sensitizing effects, we sought to determine whether 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR)-stimulated AMPK activation could prevent or reverse the deleterious effects of lipid on insulin signaling. We found that a 1-h palmitate incubation in lean myotubes reduced (P < 0.05) insulin-stimulated phosphoprotein kinase B (Akt), Akt substrate 160 (AS160), and inhibitory factor kappaBalpha (IkappaBalpha) mass, all of which were prevented with AICAR inclusion. With a longer incubation, we observed that myotubes from morbidly obese individuals appear to be largely resistant to the detrimental effects of 16 h lipid exposure as was evident, in contrast to the lean, by the absence of a reduction in insulin-stimulated insulin receptor substrate (IRS)-1 Tyr phosphorylation, phospho-Akt, and phospho-AS160 (P < 0.05). Furthermore, 16 h lipid exposure significantly reduced IkappaBalpha levels and increased phosphorylation of c-Jun NH(2)-terminal kinase (JNK) and IRS1-Ser(312) in lean myotubes only (P < 0.05). Despite a divergent response to lipid between lean and obese myotubes, AICAR inclusion improved insulin signaling in all myotubes. These findings suggest an important role for regular exercise in addition to offering a potential mechanism of action for oral AMPK-activating agents, such as thiazolidinediones and metformin.

Macrophage adiponectin expression improves insulin sensitivity and protects against inflammation and atherosclerosis

OBJECTIVE

Adiponectin is one of several important metabolically active cytokines secreted from adipose tissue. Epidemiologic studies have associated low-circulating levels of this adipokine with multiple metabolic disorders including obesity, insulin resistance, type 2 diabetes, and cardiovascular disease. To investigate adiponectin-mediated changes in metabolism in vivo, we generated transgenic mice that specifically express the gene coding for human adiponectin in mouse macrophages using the human scavenger receptor A-I gene enhancer/promoter.

METHODS AND RESULTS

Using this transgenic mouse model, we found that adiponectin expression was associated with reduced whole-animal body and fat-pad weight and an improved lipid accumulation in macrophages when these transgenic mice were fed with a high-fat diet. Moreover, these macrophage Ad-TG mice exhibit enhanced whole-body glucose tolerance and insulin sensitivity with reduced proinflammatory cytokines, MCP-1 and TNF-a (both in the serum and in the metabolic active macrophage), adipose tissue, and skeletal muscle under the high-fat diet condition. Additional studies demonstrated that these macrophage adiponectin transgenic animals exhibit reduced macrophage foam cell formation in the arterial wall when these transgenic mice were crossed with an LDL receptor-deficient mouse model and were fed a high-fat diet.

CONCLUSIONS

These results suggest that adiponectin expressed in macrophages can physiologically modulate metabolic activities in vivo by improving metabolism in distal tissues. The use of macrophages as carriers for adiponectin, a molecule with antidiabetes, anti-inflammatory, and antiatherogenic properties, provides a novel and unique strategy for studying the mechanisms of adiponectin-mediated alterations in body metabolism in vivo.

Metformin Improves Insulin Signaling in Obese Rats via Reduced IKKbeta Action in a Fiber-Type Specific Manner

Metformin is a widely used insulin-sensitizing drug, though its mechanisms are not fully understood. Metformin has been shown to activate AMPK in skeletal muscle; however, its effects on the inhibitor of kappaB kinasebeta (IKKbeta) in this same tissue are unknown. The aim of this study was to (1) determine the ability of metformin to attenuate IKKbeta action, (2) determine whether changes in AMPK activity are associated with changes in IKKbeta action in skeletal muscle, and (3) examine whether changes in AMPK and IKKbeta function are consistent with improved insulin signaling. Lean and obese male Zuckers received either vehicle or metformin by oral gavage daily for four weeks (four groups of eight). Proteins were measured in white gastrocnemius (WG), red gastrocnemius (RG), and soleus. AMPK phosphorylation increased (P < .05) in WG in both lean (57%) and obese (106%), and this was supported by an increase in phospho-ACC in WG. Further, metformin increased IkappaBalpha levels in both WG (150%) and RG (67%) of obese rats, indicative of reduced IKKbeta activity (P < .05), and was associated with reduced IRS1-pSer(307) (30%) in the WG of obese rats (P < .02). From these data we conclude that metformin treatment appears to exert an inhibitory influence on skeletal muscle IKKbeta activity, as evidenced by elevated IkappaBalpha levels and reduced IRS1-Ser(307) phosphorylation in a fiber-type specific manner.

Troglitazone inhibits vascular endothelial growth factor-induced angiogenic signaling via suppression of reactive oxygen species production and extracellular signal-regulated kinase phosphorylation in endothelial cells

Thiazolidinediones, peroxisome proliferators-activated receptor gamma (PPARgamma) ligands, have been recognized as a potential therapeutic agents for the treatment of pathological neovascularization. In the present study, we examined the molecular mechanism by which troglitazone (TROG), a PPARgamma agonist, exerts its inhibitory action in vascular endothelial growth factor (VEGF)-induced angiogenesis signaling. In an in vitro angiogenesis model using human umbilical vein endothelial cells, TROG (20 muM) significantly suppressed VEGF-induced cell proliferation and invasion of the cells into the Matrigel basement membrane, which was not reversed by treatment with PPAR antagonists, GW9662 (10 muM) and bisphenol A diglycidyl ether (10 muM). TROG also blocked VEGF-induced reactive oxygen species (ROS) production and its downstream extracellular signal-regulated kinase (ERK) phosphorylation, and this inhibitory effect was not reversed by GW9662 (10 muM). The antiangiogenic activity of TROG correlated with suppression of VEGF-induced matrix metalloproteinase (MMP)-2 and membrane type 1 (MT1)-MMP expression. In addition, the effects of TROG on VEGF-induced MMP-2 and MT1-MMP expression were comparable to those of the NADPH oxidase inhibitor diphenylene iodium (10 muM) and ERK inhibitor PD98056 (10 muM). Furthermore, in an in vivo angiogenesis system using a chick chorioallantoic membrane model, TROG dose-dependently inhibited VEGF-induced angiogenesis, which was similar to the inhibitory effect of N-acetylcysteine on VEGF-induced angiogenesis. The results suggest that the inhibitory effects of TROG on VEGF-induced angiogenesis were mediated through the suppression of VEGF-induced ROS production and ERK phosphorylation.

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.

High-fat diet induces Ikkbeta and reduces insulin sensitivity in rats with low running capacity

Rats bred for a high-capacity to run (HCR) do not develop insulin resistance on a high-fat diet (HFD) vs. those bred for a low-capacity for running (LCR). Recently, a link between obesity and insulin resistance has been established via IKKbeta action and IRS-1 Ser (312/307) phosphorylation. This study measured IkappaBalpha and IRS-1 pSer (307) in mixed gastrocnemius muscle in HCR and LCR rats challenged with a 12-wk HFD. HFD treatment resulted in significantly higher glucose and insulin levels in LCR vs. HCR rats. IkappaBalpha levels, an inverse indicator of IKKbeta activity, were lower in LCR vs. HCR rats maintained on chow diet and were reduced further following HFD in LCR rats only. IRS-1 pSer (307) in the LCR rats increased on the HFD vs. chow. We conclude that differences in glucose tolerance between LCR and HCR rats are at least partly explained by differences in IKKbeta activity and pSer (307) levels.

Peroxisome proliferator-activated receptor agonists: do they increase cardiovascular risk?

Cardiovascular disease is a major cause of morbidity and mortality among people with type 2 diabetes mellitus. The peroxisome proliferator-activated receptor (PPAR) agonists have a significant role on glucose and fat metabolism. Thiazolidinediones (TZDs) are predominantly PPARγ agonists, and their primary benefit appears to be the prevention of diabetic complications by improving glycemic control and lipid profile. Recently, the cardiovascular safety of rosiglitazone was brought to center stage following meta analyses and the interim analysis of the RECORD trial. Current evidence points to rosiglitazone having a greater risk of myocardial ischemic events than placebo, metformin, or sulfonylureas. This review article discusses the mechanism of action of PPAR agonists and correlates it with clinical and laboratory outcomes in the published literature. In addition, this review article attempts to discuss some of the molecular mechanisms regarding the association between TZDs therapy and the nontraditional cardiovascular risks.

Anti-inflammatory effect of rosiglitazone is not reflected in expression of NFkappaB-related genes in peripheral blood mononuclear cells of patients with type 2 diabetes mellitus

BACKGROUND

Rosiglitazone not only improves insulin-sensitivity, but also exerts anti-inflammatory effects. We have now examined in type 2 diabetic patients if these effects are reflected by changes in mRNA expression in peripheral blood mononuclear cells (PBMCs) to see if these cells can be used to study these anti-inflammatory effects at the molecular level in vivo.

METHOD

Eleven obese type 2 diabetic patients received rosiglitazone (2 x 4 mg/d) for 8 weeks. Fasting blood samples were obtained before and after treatment. Ten obese control subjects served as reference group. The expression of NFkappaB-related genes and PPARgamma target genes in PBMCs, plasma TNFalpha, IL6, MCP1 and hsCRP concentrations were measured. In addition, blood samples were obtained after a hyperinsulinemic-euglycemic clamp.

RESULTS

Rosiglitazone reduced plasma MCP1 and hsCRP concentrations in diabetic patients (-9.5 +/- 5.3 pg/mL, p = 0.043 and -1.1 +/- 0.3 mg/L p = 0.003), respectively). For hsCRP, the concentration became comparable with the non-diabetic reference group. However, of the 84 NFkappaB-related genes that were measured in PBMCs from type 2 diabetic subjects, only RELA, SLC20A1, INFgamma and IL1R1 changed significantly (p < 0.05). In addition, PPARgamma and its target genes (CD36 and LPL) did not change. During the clamp, insulin reduced plasma MCP1 concentration in the diabetic and reference groups (-9.1 +/- 1.8%, p = 0.001 and -11.1 +/- 4.1%, p = 0.023, respectively) and increased IL6 concentration in the reference group only (23.5 +/- 9.0%, p = 0.028).

CONCLUSION

In type 2 diabetic patients, the anti-inflammatory effect of rosiglitazone is not reflected by changes in NFkappaB and PPARgamma target genes in PBMCs in vivo. Furthermore, our results do not support that high insulin concentrations contribute to the pro-inflammatory profile in type 2 diabetic patients.

The effect of diabetes mellitus on organ dysfunction with sepsis: an epidemiological study

Introduction

Diabetes mellitus (DM) is one of the most common chronic co-morbid medical conditions in the USA and is frequently present in patients with sepsis. Previous studies reported that people with DM and severe sepsis are less likely to develop acute lung injury (ALI). We sought to determine whether organ dysfunction differed between people with and without DM and sepsis.

Methods

Using the National Hospital Discharge Survey US, sepsis cases from 1979 to 2003 were integrated with DM prevalence from the Centers for Disease Control and Prevention (CDC) Diabetes Surveillance System.

Results

During the study period 930 million acute-care hospitalisations and 14.3 million people with DM were identified. Sepsis occurred in 12.5 million hospitalisations and DM was present in 17% of patients with sepsis. In the population, acute respiratory failure was the most common organ dysfunction (13%) followed by acute renal failure (6%). People with DM were less likely to develop acute respiratory failure (9% vs. 14%, p < 0.05) and more likely to develop acute renal failure (13% vs. 7%, p < 0.05). Of people with DM and sepsis, 27% had a respiratory source of infection compared with 34% in people with no DM (p < 0.05). Among patients with a pulmonary source of sepsis, 16% of those with DM and 23% of those with no DM developed acute respiratory failure (p < 0.05); in non-pulmonary sepsis acute respiratory failure occurred in 6% of people with DM and 10% in those with no DM (p < 0.05).

Conclusions

In sepsis, people with diabetes are less likely to develop acute respiratory failure, irrespective of source of infection. Future studies should determine the relationship of these findings to reduced risk of ALI in people with DM and causative mechanisms.

Obesity-related upregulation of monocyte chemotactic factors in adipocytes: involvement of nuclear factor-kappaB and c-Jun NH2-terminal kinase pathways

OBJECTIVE

We sought to evaluate the entire picture of all monocyte chemotactic factors that potentially contribute to adipose tissue macrophage accumulation in obesity.

RESEARCH DESIGN AND METHODS

Expression and regulation of members in the entire chemokine superfamily were evaluated in adipose tissue and isolated adipocytes of obese versus lean mice. Kinetics of adipose tissue macrophage infiltration was characterized by fluorescence-activated cell sorting. The effects of fatty acids on stimulation of chemokine expression in adipocytes and underlying mechanisms were investigated.

RESULTS

Six monocyte chemotactic factors were found to be predominantly upregulated in isolated adipocytes versus stromal vascular cells in obese mice for the first time, although most of them were previously reported to be upregulated in whole adipose tissue. In diet-induced obese mice, adipose tissue enlargement, increase of adipocyte number, and elevation of multiple chemokine expression precede the initiation of macrophage infiltration. Free fatty acids (FFAs) are found to be inducers for upregulating these chemokines in 3T3-L1 adipocytes, and this effect can be partially blunted by reducing Toll-like receptor 4 expression. FFAs induce expression of monocyte chemotactic factors in adipocytes via both transcription-dependent and -independent mechanisms. In contrast to the reported role of JNK as the exclusive mediator of FFA-induced monocyte chemoattractant protein-1 (MCP-1) expression in macrophages, we show a novel role of inhibitor of kappaB kinase-beta (IKKbeta) in mediating FFA-induced upregulation of all six chemokines and a role of JNK in FFA-induced upregulation of MCP-1 and MCP-3.

CONCLUSIONS

Multiple chemokines derived from adipocytes might contribute to obesity-related WAT macrophage infiltration with FFAs as potential triggers and involvement of both IKKbeta and JNK pathways.

Mechanism for improved insulin sensitivity after gastric bypass surgery

CONTEXT

Surgical treatments of obesity have been shown to induce rapid and prolonged improvements in insulin sensitivity.

OBJECTIVE

The aim of the study was to investigate the effects of gastric bypass surgery and the mechanisms that explain the improvement in insulin sensitivity.

DESIGN

We performed a cross-sectional, nonrandomized, controlled study.

SETTING

This study was conducted jointly between the Departments of Exercise Science and Physiology at East Carolina University in Greenville, North Carolina.

SUBJECTS

Subjects were recruited into four groups: 1) lean [body mass index (BMI) < 25 kg/m(2); n = 93]; 2) weight-matched (BMI = 25 to 35 kg/m(2); n = 310); 3) morbidly obese (BMI > 35 kg/m(2); n = 43); and 4) postsurgery patients (BMI approximately 30 kg/m(2); n = 40). Postsurgery patients were weight stable 1 yr after surgery.

MAIN OUTCOME MEASURES

Whole-body insulin sensitivity, muscle glucose transport, and muscle insulin signaling were assessed.

RESULTS

Postsurgery subjects had insulin sensitivity index values that were similar to the lean and higher than morbidly obese and weight-matched control subjects. Glucose transport was higher in the postsurgery vs. morbidly obese and weight-matched groups. IRS1-pSer(312) in the postsurgery group was lower than morbidly obese and weight-matched groups. Inhibitor kappaBalpha was higher in the postsurgery vs. the morbidly obese and weight-matched controls, indicating reduced inhibitor of kappaB kinase beta activity.

CONCLUSIONS

Insulin sensitivity and glucose transport are greater in the postsurgery patients than predicted from the weight-matched group, suggesting that improved insulin sensitivity after bypass is due to something other than, or in addition to, weight loss. Improved insulin sensitivity is related to reduced inhibitor of kappaB kinase beta activity and enhanced insulin signaling in muscle.

Adipose inflammation: cause or consequence of obesity-related insulin resistance

Obesity constitutes a critical risk factor for the development of many life threatening diseases, particularly insulin resistance and type 2 diabetes. Adipose tissue plays an important role in regulating whole body energy homeostatsis and obesity-related insulin resistance. Inflammation has been commonly linked to insulin resistance. Recent studies demonstrated that adipose tissue is an important source for producing inflammatory molecules in the obese state, primarily due to accumulation of macrophages. Animal models deficient in key inflammatory molecules or with reduced adipose macrophage infiltration are protected from development of obesity-related insulin resistance. Repression of adipose inflammation may be a useful approach to ameliorate obesity-associated metabolic disorders.

Peroxisome proliferator-activated receptor-gamma agonists and diabetes: current evidence and future perspectives

Since their initial availability in 1997, the thiazolidinediones (TZDs) have become one of the most commonly prescribed classes of medications for type 2 diabetes. In addition to glucose control, the TZDs have a number of pleiotropic effects on myriad traditional and non-traditional risk factors for diabetes. TZDs may benefit cardiovascular parameters, such as lipids, blood pressure, inflammatory biomarkers, endothelial function and fibrinolytic state. In this review, we summarise the experimental, preclinical and clinical data regarding the effects of the TZDs in conditions for which they are indicated and discuss their potential in the treatment of other conditions.

Effect of pioglitazone on progression of subclinical atherosclerosis in non-diabetic premenopausal Hispanic women with prior gestational diabetes

The Pioglitazone in the Prevention of Diabetes (PIPOD) study was a single arm 3-year open-label pioglitazone treatment to determine the effects of pioglitazone in women with prior gestational diabetes mellitus (GDM) who had completed the troglitazone in the Prevention of Diabetes (TRIPOD) study. Here we report the results on progression of subclinical atherosclerosis, measured by carotid intima-media thickness (CIMT) in non-diabetic women. Data were analyzed to compare CIMT progression rates during pioglitazone treatment to rates that had been observed during either placebo or troglitazone treatment in the TRIPOD study. Sixty-one women met the entry criteria with mean age of 40 years. In the 30 women who came to PIPOD from the placebo arm of TRIPOD, the CIMT rate was 69% lower during pioglitazone treatment than it had been during placebo (0.0031 vs. 0.0100mm/yr, p=0.006). In the 31 women who came to PIPOD from the troglitazone arm of TRIPOD, CIMT rate was 38% lower during pioglitazone than it had been during troglitazone, a difference that was not statistically significant (0.0037 vs. 0.0060mm/year; p=0.26). Adjustment for differences in baseline characteristics and potential on-trial confounders did not alter the conclusion but did increase the CIMT rates differences slightly. We conclude that treatment with pioglitazone slowed CIMT progression in women who had been on placebo in the TRIPOD study and maintained a relatively low rate of progression in women who had been on troglitazone. Pioglitazone slows progression of subclinical atherosclerosis in young Hispanic women at increased risk for type 2 diabetes.

Evaluation of proinflammatory cytokines and inflammation markers as biomarkers for the action of thiazolidinediones in Type 2 diabetes mellitus patients and healthy volunteers

AIMS

Thiazolidinediones (TZDs) not only enhance cellular glucose transport but are reported to have potent anti-inflammatory effects. These effects may play an important role in the insulin sensitizing mechanism, and possibly precede the effects on parameters of glucoregulation. We sought to investigate whether these anti-inflammatory effects could yield early responding biomarkers for TZD action in Type 2 diabetes mellitus (T2DM) patients and healthy volunteers (HV) to expedite early clinical development of novel compounds.

METHODS

We investigated the timing of treatment effects on several proinflammatory cytokines and markers of inflammation in comparison with effects on typical measures of glucoregulation in T2DM patients and HV receiving rosiglitazone 4 mg or placebo twice daily for 6 weeks.

RESULTS

We found a significant reduction in interleukin (IL)-6 [-39.4%, confidence interval (CI) - 60.0, - 8.2] and white blood cell count (-18.4%, CI - 30.2, - 4.5) after 4 weeks of treatment in the T2DM group. These anti-inflammatory effects did not precede the effects on typical parameters of glucoregulation in the T2DM group and there was no significant anti-inflammatory response in the HV group.

CONCLUSION

We could not identify biomarkers that precede the effects of rosiglitazone on parameters of glucoregulation in T2DM or that have a significant response in HV. However, the IL-6 response observed in this study indicates a potential role for this cytokine as complementary biomarker in clinical 'proof of concept' studies with novel TZDs.

Is there an estrogenic component in the metabolic syndrome?

One of the major upcoming concerns leading to health related problems in the industrialized societies is the metabolic syndrome which is characterized by central obesity, hypertension, raised fasting glucose and triglyceride levels. The focus of this review is on a potential estrogenic linkage between the metabolic mechanisms involved into the development of this disease cluster and specific estrogen related regulatory pattern. The candidate molecules for this link are insulin and insulin-like growthfactor, C-reactive protein, peroxisome-proliferation-activatingreceptorgamma, and leptin which all seem to interact with each other and show a responsiveness to changing estrogen levels. From this perspective they might also represent target molecules for a phytochemical intervention with phytoestrogens.

Adipose tissue inflammation induced by high-fat diet in obese diabetic mice is prevented by n-3 polyunsaturated fatty acids

AIMS/HYPOTHESIS

Inflammatory alterations in white adipose tissue appear to underlie complications of obesity including diabetes mellitus. Polyunsaturated fatty acids (PUFA), particularly those of the n-3 series, modulate immune responses and may ameliorate insulin sensitivity. In this study, we investigated how PUFA affect white adipose tissue inflammation and gene expression in obese diabetic animals.

MATERIALS AND METHODS

We treated db/db mice as well as lean non-diabetic mice (db/+) with either low-fat standard diet (LF) or high-fat diets rich in (1) saturated/monounsaturated fatty acids (HF/S), (2) n-6 PUFA (HF/6) and (3) the latter including purified marine n-3 PUFA (HF/3).

RESULTS

Many genes involved in inflammatory alterations were upregulated in db/db mice on HF/S compared with LF in parallel with phosphorylation of c-Jun N-terminal kinase (JNK). In parallel, adipose tissue infiltration with macrophages was markedly enhanced by HF/S. When compared with HF/S, HF/6 showed only marginal effects on adipose tissue inflammation. However, inclusion of n-3 PUFA in the diet (HF/3) completely prevented macrophage infiltration induced by high-fat diet and changes in inflammatory gene expression, also tending to reduce JNK phosphorylation (p<0.1) in diabetic mice despite unreduced body weight. Moreover, high-fat diets (HF/S, HF/6) downregulated expression and reduced serum concentrations of adiponectin, but this was not the case with n-3 PUFA.

CONCLUSIONS/INTERPRETATION

n-3 PUFA prevent adipose tissue inflammation induced by high-fat diet in obese diabetic mice, thereby dissecting obesity from adipose tissue inflammation. These data suggest that beneficial effects of n-3 PUFA on diabetes development could be mediated by their effect on adipose tissue inflammation.

Chronic Obstructive Pulmonary Disease, inflammation and co-morbidity--a common inflammatory phenotype?

Chronic Obstructive Pulmonary Disease (COPD) is and will remain a major cause of morbidity and mortality worldwide. The severity of airflow obstruction is known to relate to overall health status and mortality. However, even allowing for common aetiological factors, a link has been identified between COPD and other systemic diseases such as cardiovascular disease, diabetes and osteoporosis.

COPD is known to be an inflammatory condition and neutrophil elastase has long been considered a significant mediator of the disease. Pro-inflammatory cytokines, in particular TNF-α (Tumour Necrosis Factor alpha), may be the driving force behind the disease process. However, the roles of inflammation and these pro-inflammatory cytokines may extend beyond the lungs and play a part in the systemic effects of the disease and associated co-morbidities. This article describes the mechanisms involved and proposes a common inflammatory TNF-α phenotype that may, in part, account for the associations.

Reduced skeletal muscle inhibitor of kappaB beta content is associated with insulin resistance in subjects with type 2 diabetes: reversal by exercise training

Skeletal muscle insulin resistance plays a key role in the pathogenesis of type 2 diabetes. It recently has been hypothesized that excessive activity of the inhibitor of kappaB (IkappaB)/nuclear factor kappaB (NFkappaB) inflammatory pathway is a mechanism underlying skeletal muscle insulin resistance. However, it is not known whether IkappaB/NFkappaB signaling in muscle from subjects with type 2 diabetes is abnormal. We studied IkappaB/NFkappaB signaling in vastus lateralis muscle from six subjects with type 2 diabetes and eight matched control subjects. Muscle from type 2 diabetic subjects was characterized by a 60% decrease in IkappaB beta protein abundance, an indicator of increased activation of the IkappaB/NFkappaB pathway. IkappaB beta abundance directly correlated with insulin-mediated glucose disposal (Rd) during a hyperinsulinemic (40 mU x m(-2) x min(-1))-euglycemic clamp (r = 0.63, P = 0.01), indicating that increased IkappaB/NFkappaB pathway activity is associated with muscle insulin resistance. We also investigated whether reversal of this abnormality could be a mechanism by which training improves insulin sensitivity. In control subjects, 8 weeks of aerobic exercise training caused a 50% increase in both IkappaB alpha and IkappaB beta protein. In subjects with type 2 diabetes, training increased IkappaB alpha and IkappaB beta protein to levels comparable with that of control subjects, and these increments were accompanied by a 40% decrease in tumor necrosis factor alpha muscle content and a 37% increase in insulin-stimulated glucose disposal. In summary, subjects with type 2 diabetes have reduced IkappaB protein abundance in muscle, suggesting excessive activity of the IkappaB/NFkappaB pathway. Moreover, this abnormality is reversed by exercise training.

Activation of peripheral blood CD14+ monocytes occurs in diabetes

Blood levels of inflammatory markers associated with endothelial dysfunction and atherosclerosis are increased in diabetic patients; the highest levels occur in poorly controlled diabetes. We investigated the activation state of peripheral blood monocytes in diabetes with respect to scavenger receptor (CD36) expression and monocyte chemoattractant protein-1, intracellular adhesion molecule-1, vascular cell adhesion molecule-1, and peroxisome proliferator-activated receptors mRNA expression. CD14(+) monocytes were isolated from peripheral blood of type 1 and type 2 diabetic patients with good (HbA(1c) <7.0%) or poor (>9.4%) glycemic control and a group of nondiabetic subjects. Monocytes from diabetic subjects displayed increased CD36 cell surface expression (P < 0.0005) and increased uptake of oxidized LDL (P < 0.05). Monocyte chemoattractant protein-1 gene expression was increased in monocytes from both groups of diabetic subjects (P < 0.05). Both CD68 and peroxisome proliferator-activated receptor-gamma gene expression were increased in the poorly controlled diabetic group (P < 0.05 for each), whose monocytes also displayed increased attachment to endothelial monolayers (P < 0.0005 vs. nondiabetic control subjects). In poorly controlled diabetes, CD14(+) monocytes are functionally activated and show some of the differentiation markers associated with macrophages. These monocytes also demonstrate an increased ability for attachment to normal endothelial cells, one of the early stages in atherogenesis.

Effect of a peroxisome proliferator-activated receptor-gamma agonist on myocardial blood flow in type 2 diabetes

OBJECTIVE

The relationship between coronary endothelial function and insulin resistance remains speculative. We sought to determine whether pioglitazone, an insulin-sensitizing peroxisome proliferator-activated receptor (PPAR)-gamma agonist, improves cardiac endothelial function in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Sixteen subjects with insulin-treated type 2 diabetes and without overt cardiovascular disease were randomly assigned to receive either 45 mg of pioglitazone or matching placebo for 3 months. Rest and adenosine-stimulated myocardial blood flow (MBF) were quantified with [(13)N]ammonia and positron emission tomography at baseline and study conclusion.

RESULTS

After 3 months, HbA(1c) levels dropped by 0.68% in the pioglitazone group and increased by 0.17% in the placebo group (P = 0.009 for difference between groups). Triglyceride (-93 vs. -39 mg/dl, P = 0.026) and HDL concentrations (+4.8 vs. -6.0 mg/dl, P = 0.014) improved significantly in the pioglitazone group compared with placebo. Despite these favorable changes, there was no demonstrable change in baseline MBF (-0.05 +/- 0.24 vs. -0.09 +/- 0.24 ml . min(-1) . g(-1), P = 0.45), adenosine-stimulated MBF (0.10 +/- 0.75 vs. 0.14 +/- 0.31 ml . min(-1) . g(-1), P = 0.25), or coronary flow reserve (0.45 +/- 1.22 vs. 0.35 +/- 0.72 ml . min(-1) . g(-1), P = 0.64) after 12 weeks of exposure to pioglitazone or placebo, respectively. Regression analysis revealed that lower glucose concentration at the time of the study was associated with higher coronary flow reserve (P = 0.012).

CONCLUSIONS

Pioglitazone treatment for 12 weeks in subjects with insulin-requiring type 2 diabetes had no demonstrable effect on coronary flow reserve despite metabolic improvements. Higher ambient glucose levels contribute to impaired vascular reactivity in individuals with diabetes.

Inflammatory markers in women with a recent history of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a risk factor for both Type 2 diabetes (DM2) and insulin-resistance syndrome (IRS). C-reactive protein (CRP), fibrinogen and leukocyte count are increased in the IRS and predict DM2 and cardiovascular disease (CVD). The chemochine monocyte chemoattractant protein-1 (MCP-1/CCL2) is also elevated in DM2 and CVD. Recent evidence suggests a relation between chronic inflammation and GDM, but post-delivery information on inflammatory markers in these high-risk women is lacking. Serum levels of CRP, fibrinogen, MCP-1/ CCL2, and leukocyte blood count have been assessed in 26 women with and 26 women without a recent history of GDM, matched for age, body mass index (BMI), post-partum duration and parity. DM2 was excluded in all the participants by an oral glucose tolerance test (OGTT). Women with previous GDM showed significantly higher CRP (p=0.007) and fibrinogen (p=0.02) serum concentrations, whereas MCP-1/CCL2 serum levels and leukocyte blood count were comparable in the two groups. Overall, CRP levels significantly correlated with BMI (r=0.40, p=0.03), waist-to-hip ratio (WHR) (r=0.44, p=0.001), fasting insulin (r=0.27, p=0.04), insulin-resistance assessed by means of the homeostatic model (HOMA) (r=0.28, p=0.04), and fibrinogen concentration (r=0.49, p=0.0001). At linear regression analysis, only WHR and fibrinogen were independently associated with CRP levels. In conclusion, the increase of inflammatory markers may be one of the first detectable disorders in healthy women at high risk of DM2 and IRS, like those with a GDM history.

Stress-hyperglycemia, insulin and immunomodulation in sepsis

Stress-hyperglycemia and insulin resistance are exceedingly common in critically ill patients, particularly those with sepsis. Multiple pathogenetic mechanisms are responsible for this metabolic syndrome; however, increased release of pro-inflammatory mediators and counter-regulatory hormones may play a pivotal role. Recent data suggests that hyperglycemia may potentiate the pro-inflammatory response while insulin has the opposite effect. Furthermore, emerging evidence suggests that tight glycemic control will improve the outcome of critically ill patients. This paper reviews the pathophysiology of stress hyperglycemia in the critically ill septic patient and outlines a treatment strategy for the management of this disorder.

Inflammation and glucose intolerance: a prospective study of gestational diabetes mellitus

OBJECTIVE

Increased leukocyte count is a marker of inflammation that has been associated with the development of type 2 diabetes in prospective studies. Although gestational diabetes mellitus (GDM) and type 2 diabetes share certain pathophysiological mechanisms, few studies have examined inflammation and risk of GDM.

RESEARCH DESIGN AND METHODS

We prospectively examined routine leukocyte counts collected at the first prenatal visit in a cohort of 2,753 nulliparous euglycemic women, 98 (3.6%) of whom were later diagnosed with GDM. Subjects were divided into quartiles of leukocyte count, and the results of third-trimester glucose screening tests and the incidence of GDM among these quartiles were compared. Logistic regression was used to calculate univariate and multivariable-adjusted relative risks (RRs) of GDM according to leukocyte quartiles.

RESULTS

Leukocyte counts were increased among women who subsequently developed GDM compared with those who remained free of GDM (10.5 +/- 2.2 vs. 9.2 +/- 2.2 x 10(3) cells/ml; P < 0.01). There was a linear increase in postloading mean glucose levels (P for trend <0.01), the area under the glucose tolerance test curves (P for trend <0.01), and the incidence of GDM (quartile 1, 1.1; quartile 2, 2.5; quartile 3, 4.2; and quartile 4, 6.4%; P for trend <0.01) with increasing leukocyte quartiles. In the multivariable-adjusted analysis, the linear trend in the RR of GDM with increasing leukocyte quartiles remained statistically significant (quartile 1, reference; quartile 2, RR 2.3 [95% CI 0.9-5.7]; quartile 3, 3.3 [1.4-7.8]; quartile 4, 4.9 [2.1-11.2]; P for trend <0.01).

CONCLUSIONS

Increased leukocyte count early in pregnancy is independently and linearly associated with the results of GDM screening tests and the risk of GDM. Although overlap in the leukocyte count distributions precludes it from being a clinically useful biomarker, these data suggest that inflammation is associated with the development of GDM and may be another pathophysiological link between GDM and future type 2 diabetes.

Elevation of free fatty acids induces inflammation and impairs vascular reactivity in healthy subjects

To test the possible acute proinflammatory effects of fatty acids, we induced an increase in plasma free fatty acid (FFA) concentrations after a lipid and heparin infusion for 4 h in 10 healthy subjects. We determined the nuclear factor-kappaB (NF-kappaB) binding activity in mononuclear cells (MNCs), the p65 subunit of NF-kappaB, reactive oxygen species (ROS) generation by MNC, and polymorphonuclear leukocytes (PMN). Brachial artery reactivity, using postischemic flow-mediated dilation, was also measured. NF-kappaB binding activity in the MNC nuclear extracts increased to 163 +/- 17% and 144 +/- 14% as compared with basal levels at 2 and 4 h (P < 0.005) and remained elevated (P < 0.05) at 6 h (2 h after cessation of lipid infusion). NF-kappaB p65 subunit protein expression in MNC homogenates also increased at 2, 4, and 6 h (P < 0.05). ROS generation by PMNs increased significantly at 2 and 4 h (P < 0.005), whereas that by MNCs increased at 4 h (P < 0.05). Plasma macrophage migration inhibitory factor increased at 2 (P < 0.05) and 4 h (P < 0.005), respectively, and declined to baseline at 6 h. The postischemic flow-mediated dilation of brachial artery decreased from 6.3 +/- 1.1% at baseline to 4.3 +/- 1.9% and 2.7 +/- 2.1% (P < 0.01) at 2, 4, and 6 h, respectively. We conclude that an increase in FFA concentration induces oxidative stress and has a proinflammatory effect; it also impairs postischemic flow-mediated vasodilation of the brachial artery.

Fasting plasma leptin, tumor necrosis factor-alpha receptor 2, and monocyte chemoattracting protein 1 concentration in a population of glucose-tolerant and glucose-intolerant women: impact on cardiovascular mortality

OBJECTIVE

Leptin and tumor necrosis factor (TNF)-alpha are associated with insulin resistance and cardiovascular disease. In vitro studies suggested that these effects may be mediated via overproduction of monocyte chemoattracting protein (MCP)-1/CCL2, which is a chemokine involved in the pathogenesis of atherosclerosis.

RESEARCH DESIGN AND METHODS

In this study, fasting plasma leptin, soluble TNF-alpha receptor 2 (TNF-alpha-R2), and MCP-1/CCL2 concentrations were measured in 207 middle-aged women (age 61 +/- 12 years, BMI 30.1 +/- 6.6 kg/m(2)), including 53 patients with type 2 diabetes, 42 with impaired glucose tolerance, and 112 with normal glucose tolerance, to assess cross-sectionally their relationship with markers of atherosclerosis and, longitudinally over 7 years, whether their circulating levels were associated with cardiovascular disease (CVD) mortality.

RESULTS

At baseline, leptin and TNF-alpha-R2 were not different among groups; meanwhile, MCP-1/CCL2 was increased in type 2 diabetes (P < 0.05). All showed significant associations with biochemical risk markers of atherosclerosis. In a univariate analysis, age, fasting insulin, leptin, and MCP-1/CCL2 were associated with CVD mortality at 7 years. When a multivariate analysis was performed, only age, leptin, and insulin retained an independent association with CVD mortality, with leptin showing a protective effect (hazard ratio 0.88; P < 0.02).

CONCLUSIONS

In middle-aged women, MCP-1/CCL2, leptin, and TNF-alpha-R2 were all related to biochemical risk markers of atherosclerosis. MCP-1/CCL2 concentration was the only one to be increased in type 2 diabetes with respect to nondiabetic women and the only one to be associated with increased risk of CVD mortality after a 7-year follow-up period in the univariate analysis. In the multivariate analysis, neither MCP-1/CCL2 nor TNF-alpha-R2 was associated with CVD mortality, and inspection of the data showed that leptin, in both the univariate and multivariate analysis, was associated with a protective effect.

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.