Effects of hyperglycemia and hyperinsulinemia on circulating tissue factor procoagulant activity and platelet CD40 ligand

Hyperglycemia is associated with enhanced thrombin formation, platelet activation, and fibrin clot resistance to lysis in patients with acute coronary syndrome

OBJECTIVE

Acute hyperglycemia on admission for acute coronary syndrome worsens the prognosis in patients with and without known diabetes. Postulated mechanisms of this observation include prothrombotic effects. The aim of this study was to evaluate the effect of elevated glucose levels on blood clotting in acute coronary syndrome patients.

RESEARCH DESIGN AND METHODS

We studied 60 acute coronary syndrome patients within the first 12 h after pain onset, including 20 subjects with type 2 diabetes, 20 subjects with no diagnosed diabetes but with glucose levels >7.0 mmol/l, and 20 subjects with glucose levels <7.0 mmol/l. We determined generation of thrombin-antithrombin complexes (TATs) and soluble CD40 ligand (sCD40L), a platelet activation marker, at the site of microvascular injury, together with ex vivo plasma fibrin clot permeability and lysis time.

RESULTS

The acute coronary syndrome patients with no prior diabetes but elevated glucose levels had increased maximum rates of formation and total production of TATs (by 42.9%, P < 0.0001, and by 25%, P < 0.0001, respectively) as well as sCD40L release (by 16.2%, P = 0.0011, and by 16.3%, P < 0.0001, respectively) compared with those with normoglycemia, whereas diabetic patients had the highest values of TATs and sCD40L variables (P < 0.0001 for all comparisons). Patients with hyperglycemia, with no previously diagnosed diabetes, had longer clot lysis time (by approximately 18%, P < 0.0001) similar to that in diabetic subjects, but not lower clot permeability compared with that in normoglycemic subjects.

CONCLUSIONS

Hyperglycemia in acute coronary syndrome is associated with enhanced local thrombin generation and platelet activation, as well as unfavorably altered clot features in patients with and without a previous history of diabetes.

Effect of insulin therapy on coagulation and fibrinolysis in medical intensive care patients

OBJECTIVE

Most intensive care deaths beyond the first few days of critical illness are attributable to nonresolving organ failure, either due to or coinciding with sepsis. One of the mechanisms that is thought to contribute to the pathogenesis of organ failure is microvascular thrombosis. Recently, we reported significant improved survival and prevention of organ failure with the use of intensive insulin therapy to maintain normoglycemia for at least several days. We hypothesize that intensive insulin therapy also prevents severe coagulation abnormalities thereby contributing to less organ failure and better survival.

DESIGN

This was a preplanned subanalysis of a large randomized controlled study, conducted at a university hospital medical intensive care unit. The intervention was strict blood glucose control to normoglycemia with insulin.

RESULTS

Mortality of intensive insulin-treated patients was lower than that of conventionally treated patients for all classes of upon-admission disseminated intravascular coagulation (DIC) scores, except for those patients with overt DIC scores of 6 or higher (for DIC < 5, p = 0.003; for DIC > or = 5, p = 0.4). There was no effect of insulin therapy on any of the fibrinolytic, coagulation, or inflammatory parameters tested.

CONCLUSIONS

This negative observation does not support a key role for these systems in explaining the clinical benefit of intensive insulin therapy, although a short-lived effect within 5 days of treatment cannot be excluded.

The proinflammatory mediator CD40 ligand is increased in the metabolic syndrome and modulated by adiponectin

OBJECTIVES

We hypothesized that the CD40/CD40 ligand (CD40L) system is up-regulated in the metabolic syndrome (MS) and modulated by adiponectin (AN). The objectives were: 1) to compare plasma and monocyte CD40L in patients with MS and controls and its association with clinical and biochemical parameters, 2) to investigate platelets as a source of soluble CD40L (sCD40L), and 3) to analyze the effects of AN on CD40/CD40L.

METHODS

Plasma sCD40L and AN were measured in 246 controls and 128 patients with MS by ELISA. Monocyte CD40/CD40L expression and platelet CD40L content and release were compared in patients with MS and controls. Monocytes and endothelial cells were cultured with AN and CD40/CD40L expression determined by real-time RT-PCR and Western blotting.

RESULTS

Patients with MS had higher sCD40L and lower AN levels than controls (0.89 +/- 0.1 vs. 0.76 +/- 0.07 ng/ml and 10.10 +/- 0.65 vs. 12.99 +/- 0.80 microg /ml, P < 0.05). Monocyte CD40/CD40L expression was higher (P < 0.05) in patients than controls (CD40: 1.31 +/- 0.31 vs. 0.80 +/- 0.14 arbitrary units; CD40L: 1.24 +/- 0.85 vs. 0.43 +/- 0.14 pg/microg protein). No differences were observed on CD40L content between resting platelets from patients with MS and controls (7.7 +/- 3.5 vs. 7.2 +/- 2.2 pg/microg protein). Stimulated platelets from patients with the MS released more (P < 0.05) sCD40L than controls (582 +/- 141 vs. 334 +/- 60% change vs. nonstimulated platelets). AN reduced CD40L mRNA and protein expression in monocytes from MS patients and endothelial cells.

CONCLUSIONS

The enhanced sCD40L and cellular CD40L expression in the MS suggests that CD40L is of pathophysiological relevance in MS. Also, a new antiinflammatory effect of AN is described through the modulation of the CD40/CD40L system.

Study of factor VII, tissue factor pathway inhibitor and monocyte tissue factor in noninsulin-dependent diabetes mellitus

Changes in plasma tissue factor (TF)-activated factor VII (FVIIa) and plasma tissue factor pathway inhibitor (TFPI) in type II diabetes mellitus are assessed, vascular complicated and noncomplicated patients compared, and whether these novel hemostatic activity markers predict vascular complications in diabetic patients, improving risk assessment, is determined. Fifty type II diabetic patients and 20 healthy controls (age, sex and body mass matched) underwent medical history and examination, fasting plasma glucose level, glycosylated hemoglobin (HbA1c), lipid profile, hemostatic parameters, plasma TF activity, and TFPI and TF expression on blood monocytes. Mean TF, TF activity, TFPI, and FVIIa significantly increased among hyperlipidemic compared with normolipidemic diabetic patients, and normolipidemic diabetic patients compared with controls. Mean percentage TF-positive monocytes with and without lipopolysaccharide, plasma TF activity, TFPI and FVIIa were significantly higher among complicated than noncomplicated diabetic patients. Mean percentage TF-positive monocytes without and with lipopolysaccharide, plasma TF activity, plasma TFPI and FVIIa were higher among diabetic patients with macrovascular compared with microvascular complications. High significant correlation occurred between HbA1c, triglycerides and percentage TF-positive monocytes with and without lipopolysaccharide stimulation, plasma TF activity and both FVIIa and TFPI. High activity levels of plasma TF and FVIIa with increased circulating TF-positive monocytes occurred in type II diabetic patients, especially with vascular complications. Results reflect high procoagulant activity possibly involved in diabetic vascular complications. Elevated TFPI levels were observed, but were not sufficient to balance high procoagulant activity. Correlation of procoagulant activity markers with HbA1c reinforces the importance of optimal glycemic control in type II diabetes.

Hyperglycemia accelerates arterial thrombus formation and attenuates the antithrombotic response to endotoxin in mice

Recent human studies reveal that hyperglycemia induces procoagulant and antifibrinolytic effects in blood that may contribute to a greater risk of arterial thrombosis, but the direct relationship between high blood glucose levels and thrombosis has not yet been investigated. We performed a number of experiments to clarify whether hyperglycemia was causally related to arterial thrombosis and whether the combined stimulus of hyperglycemia and inflammation would enhance the thrombotic effect. In a model of ferric-chloride-induced carotid artery thrombosis, hyperglycemia did not influence the time to occlusion in mice pretreated with streptozotocin, but the rate of thrombus formation was accelerated. This effect was associated with increased thrombin generation and could not be explained by changes in vessel-wall tissue factor activity. The prothrombotic effect of hyperglycemia was assessed in a separate experiment, showing that collagen/thrombin-induced platelet procoagulant activity was increased in hyperglycemic mice. The effect of inflammation was studied by injecting a low dose of endotoxin that caused a systemic inflammatory state after 24 h (increased plasma levels of tumor necrosis factor alpha, interleukin-6 and monocyte chemotactic protein 1 in diabetic and nondiabetic mice) associated with a mild delay in thrombus formation. This reduced rate of thrombus formation was attenuated by hyperglycemia. Together, these data establish a discrete but clear contribution of hyperglycemia in experimental arterial thrombosis.

Challenges for modeling and interpreting the complex biology of severe injury and inflammation

Human injury is associated with inflammatory responses that are modulated by the acute and chronic activity of endogenous factors and exogenous interventions. A characteristic feature of chronic, severe inflammatory states is the diminished signal output variability of many organ systems, including innate immune responsiveness and endogenous neural and endocrine-mediated functions. The attenuation of signal/response variability and integration of feedback capacity may contribute to systemic and tissue-specific deterioration of function. Some well-intentioned therapies directed toward support of systemic and tissue functions may actually promote the loss of system(s) adaptability and contribute to adverse outcomes in severely stressed patients. In vivo and in silico models of stress, injury, and infection have yet to fully define the influences of ongoing stressful stimulae as well as genetic variation and epigenetic factors in the context of an evolving inflammatory state. Experimental and human models incorporating variable, antecedent stress(es) and altered neuroendocrine rhythms might approximate the altered adaptability in immune and organ function responses. Such models may also provide insights into the salient mechanisms of risk and outcome more precisely than do the constrained study conditions of current animal or human models of systemic inflammation.

Tissue factor activities of streptozotocin induced diabetic rat tissues and the effect of peanut consumption

BACKGROUND

Tissue factor (TF) is considered to be a major regulator of normal haemostasis and thrombosis. Circulating TF activity is suggested to be associated with diabetes mellitus. Various tissues and body fluids have TF activity. The aim of the present study was to investigate the TF activity of streptozotocin (STZ) induced diabetic rat tissues. Peanut consumption is reported to be associated with decreased risk of type 2 diabetes. Therefore, the effect of peanut consumption on the TF activity of STZ induced diabetic rat tissues, and haemostatic parameters such as protrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen levels were determined.

METHODS

Twenty-four Wistar rats were divided into 3 groups of 8 rats each as control, STZ-induced diabetic and diabetic + peanut group. Twelve weeks later, TF activity of liver, kidney, spleen, heart, kidney, lung, pancreas and aorta and haemostatic parameters were determined.

RESULTS

In the diabetic group, TF activities of liver, kidney and spleen increased (p < 0.01) whereas the TF activity of brain decreased (p < 0.01) compared to the control group. Peanut consumption in the diabetic group decreased the TF activity of spleen and aorta (p < 0.01; p < 0.05). Haemostatic parameters did not change significantly in the groups.

CONCLUSION

Elevated TF activity in diabetic rat tissues, may contribute to the increased risk of atherothrombotic disease that accompanies the diabetic complications whereas the decreased brain TF activity may be due to a different haemostatic mechanism to protect this vital organ from the diabetic status. The decreased TF activity of peanut given diabetic rat tissues might protect these tissues from the risk of thrombosis.

Persistent platelet activation in patients with type 2 diabetes treated with low doses of aspirin

BACKGROUND

The percentage of diabetic patients who do not benefit from the protective effect of aspirin is larger than in other populations at cardiovascular risk.

OBJECTIVE

We compared the ability of aspirin to suppress TxA2 and platelet activation in vivo, in type-2 diabetics vs. high-risk non-diabetic patients.

METHODS

Urinary 11-dehydro-TXB2, plasma sCD40 L, and sP-selectin were measured, together with indices of low-grade inflammation, glycemic control, and lipid profile, in 82 patients with type-2 diabetes and 39 without diabetes, treated with low doses of aspirin.

RESULTS

Urinary 11-dehydro-TxB2, plasma sCD40L and sP-selectin were significantly higher in diabetics than in controls: [38.9 (27.8-63.3) vs. 28.5 (22.5-43.9) ng mmol(-1) of creatinine, P = 0.02], [1.06 (0.42-3.06) vs. 0.35 (0.22-0.95) ng mL(-1); P = 0.0001], [37.0 (16.8-85.6) vs. 20.0 (11.2-35.6) ng mL(-1), P = 0.0001], respectively. The proportion of individuals with diabetes increased across quartiles of 11-dehydro-TxB2, sCD40L, and sP-selectin, with the highest quartiles of 11-dehydro-TxB2, sCD40L and sP-selectin, including 66%, 93.3%, and 93.3% of individuals with diabetes. Markers of platelet activation positively correlated with indices of glycemic control but not with markers of low-grade inflammation.

CONCLUSIONS

Platelet dysfunction associated with insufficient glycemic control, may mediate persistent platelet activation under aspirin treatment.

Circulating tissue factor procoagulant activity and thrombin generation in patients with type 2 diabetes: effects of insulin and glucose

CONTEXT

Type 2 diabetes mellitus (T2DM) is a hypercoagulable state. Tissue factor (TF) is the principal initiator of blood coagulation.

OBJECTIVE

Our objective was to examine the effects of hyperglycemia and hyperinsulinemia on the TF pathway of blood coagulation in T2DM.

DESIGN

Three study protocols were used: 1) acute correction of hyperglycemia (with iv insulin) followed by 24 h of euglycemia, 2) 24 h of selective hyperinsulinemia, and 3) 24 h of combined hyperinsulinemia and hyperglycemia.

SETTING

The study took place at a clinical research center.

STUDY PARTICIPANTS

Participants included 18 T2DM patients and 22 nondiabetic controls.

RESULTS

Basal TF-procoagulant activity (TF-PCA), monocyte TF mRNA, plasma coagulation factor VII (FVIIc), and thrombin-anti-thrombin complexes were higher in T2DM than in nondiabetic controls, indicating a chronic procoagulant state. Acutely normalizing hyperglycemia over 2-4 h resulted in a small ( approximately 7%) but significant decline in TF-PCA with no further decline over 24 h. Raising insulin levels alone raised TF-PCA by 30%, whereas raising insulin and glucose levels together increased TF-PCA (by 80%), thrombin-anti-thrombin complexes, and prothrombin fragment 1.2. Plasma FVIIa and FVIIc declined with increases in TF-PCA.

CONCLUSION

We conclude that the combination of hyperglycemia and hyperinsulinemia, common in poorly controlled patients with T2DM, contributes to a procoagulant state that may predispose these patients to acute cardiovascular events.

Long-term effects of pioglitazone versus gliclazide on hepatic and humoral coagulation factors in patients with type 2 diabetes

This study compared the long-term effects of pioglitazone and gliclazide on the production of coagulation factors in patients with type 2 diabetes. Patients (n=283) with glycosylated haemoglobin > 7.5% were randomised to receive either pioglitazone (30-45 mg/day) or gliclazide (80-320 mg/day) for one year. Coagulation factors were measured at baseline and at six and 12 months. While both pioglitazone and gliclazide induced a comparable improvement in glycaemic control, only pioglitazone improved insulin sensitivity. Pioglitazone significantly (p < or = 0.001) decreased circulating levels of von Willebrand factor (-9.7%, -9.4%) and plasminogen activator inhibitor-1 (-16.8 ng/ml, -12.3 ng/ml), and increased levels of antithrombin-III (+1.3 mg/dL, +1.5 mg/dL) after six and 12 months, respectively. The beneficial effects of pioglitazone on glycaemic control, lipid homeostasis, and coagulation and thrombosis, may improve vascular outcomes in patients with type 2 diabetes.

Relaxin expression correlates significantly with serum fibrinogen variation in response to antidiabetic treatment in women with type 2 diabetes mellitus

AIM

Diabetes is associated with aberrant coagulation. Relaxin, an insulin-like peptide hormone, is a candidate to be involved in the underlying molecular mechanisms. Therefore, the present study investigated the correlation of relaxin expression with fibrinogen levels in diabetes patients undergoing oral antidiabetic treatment.

METHOD

In total, 192 type 2 diabetes patients were enrolled into the study. The patients were randomized to receive either pioglitazone or glimepiride for 26 weeks. Blood was drawn at baseline and at the end of the study to measure the concentrations of relaxin and fibrinogen with an enzyme-linked immunosorbent assay and a turbimetric method, respectively. In addition, platelets were counted at both time points.

RESULTS

Total datasets were available from 161 patients (age 62.5 +/- 8.1 years, mean +/- standard deviation; 58 women, 103 men). The median initial parameter concentrations were: relaxin, 27.4 pg/ml (range 0.4 - 380 pg/ml); fibrinogen, 3.0 g/l (range 1.1 - 7.9 g/l); platelets, 217,000/microl (range 51,000 - 547 000/microl). The data were analyzed according to the increase or decrease of each parameter after therapy compared with baseline. There was a significant correlation of relaxin variation with fibrinogen variation, seen particularly in the female subgroup (p < 0.05). The correlation was independent of the antidiabetic medication.

CONCLUSION

The data suggest that there is a correlation between fibrinogen levels and relaxin expression. Relaxin may exert its cardioprotective properties after pathologic fibrinogen increase. This regulation may be affected by diabetes. As a consequence, cardiovascular risk may increase in women with aberrant relaxin functionality.

Effects of hyperglycemia and hyperinsulinemia on the tissue factor pathway of blood coagulation

Tissue factor (TF) is the primary initiator of blood coagulation. Circulating TF procoagulant activity (TF-PCA) is associated with blood cells and microparticles and is elevated in patients with type 2 diabetes mellitus. Combined hyperinsulinemia and hyperglycemia and to a lesser degree selective hyperinsulinemia for 24 hours in healthy volunteers increased circulating TF-PCA, monocyte TF surface expression and mRNA, plasma thrombin generation, and coagulation factors VII and VIII activities, suggesting that the coagulation system had been activated. In addition, platelet CD40L and platelet-monocyte aggregates increased, indicating platelet activation. Somatostatin abolished these changes. We conclude that hyperinsulinemia, but particularly the combination of hyperinsulinemia and hyperglycemia, creates a prothrombotic state and may, in addition, be proinflammatory and proatherogenic by virtue of the actions of CD40L and TF.

Differential effects of somatostatin on circulating tissue factor procoagulant activity and protein

The tissue factor (TF) pathway is the primary mechanism for initiation of blood coagulation. Circulating blood contains TF, which originates mainly from monocytes and is thrombogenic. The presence of somatostatin (SMS) receptors on monocytes suggests the possibility that SMS may regulate TF synthesis and/or release. Circulating TF procoagulant activity (TF-PCA), factor VIIa activity (FVIIa; clotting assays), TF antigen (TF-Ag; ELISA), prothrombin fragment 1.2 (F1.2), thrombin-antithrombin complexes (ELISAs), CD40 ligand expression on platelets, and monocyte-platelet aggregates (flow cytometry) were determined in blood from normal volunteers undergoing 24 h of basal glucose/basal insulin (BG/BI) clamps and high-glucose/high-insulin (HG/HI) clamps with and without SMS. Infusions of SMS under basal conditions (BG/BI) raised TF-PCA 1.8-fold (P < 0.03), TF-Ag 2.3-fold (P < 0.001), and TF expression on monocytes by 36% (P < 0.001) and decreased plasma levels of FVIIa by 30% (P < 0.001). Infusion of SMS reduced the 8.6-fold HG/HI-induced increase in TF-Ag by 26% and the 8.6-fold increase in TF-PCA by 100%. SMS also prevented the 60% increase in TF expression on monocytes, the 2.2-fold increase in F1.2, the 40% increase in CD40L expression on platelets, and the 17% increase in monocyte-platelet aggregates seen during HG/HI. We conclude that SMS completely prevented HG/HI-induced TF activation in normal volunteers and may be of use to reduce the procoagulant state and acute vascular events in hyperinsulinemic insulin-resistant patients with type 2 diabetes.

Platelet and monocyte activation by hyperglycemia and hyperinsulinemia in healthy subjects

Type 2 diabetes mellitus (T2DM) patients have hyperglycemia and hyperinsulinemia and increased risk of atherosclerosis and acute vascular complications. We have reported elevated circulating tissue factor procoagulant activity (TF-PCA) during hyperglycemia (HG) and hyperinsulinemia (HI) in normal subjects. To evaluate the effect of hyperglycemia and hyperinsulinemia on blood cell activation, we assessed platelet CD40L and P-selectin, monocyte tissue factor (TF), and the formation of monocyte-platelet and neutrophil-platelet aggregates. These were assessed in the resting state and following activation with ADP and thrombin (SFLLRN). Healthy individuals were subjected to 24 h of hyperglycemia and hyperinsulinemia, selective hyperglycemia, selective hyperinsulinemia, or normal glucose and insulin. Platelet CD40L expression increased with high glucose/high insulin, selective hyperglycemia and selective hyperinsulinemia. Monocyte-platelet aggregates increased with high glucose/high insulin. Monocyte TF expression increased with high glucose/high insulin and with selective hyperinsulinemia. Upon stimulation with ADP and SFLLRN, monocyte-platelet and neutrophil-platelet aggregates, platelet CD40L and P-selectin, and monocyte TF increased compared to the resting state but was not different between 0 and 24 h, indicating that the responsiveness to those agonists was not altered.

CONCLUSIONS

Hyperglycemia-hyperinsulinemia in healthy individuals induced platelet activation and monocyte TF expression promoting a procoagulant and proinflammatory state that may contribute to acute vascular events and atherogenesis. Platelet responsiveness to activation with ADP or SFLLRN appears not to be altered by hyperglycemia-hyperinsulinemia.

The platelet as a therapeutic target for treating vascular diseases and the role of eicosanoid and synthetic PPARgamma ligands

The platelet was traditionally thought only to serve as the instigator of thrombus formation, but now is emerging as a pivotal player in cardiovascular disease and diabetes by inciting and maintaining inflammation. Upon activation, platelets synthesize eicosanoids such as thromboxane A2 (TXA2) and PGE2 and release pro-inflammatory mediators including CD40 ligand (CD40L). These mediators activate not only platelets, but also stimulate vascular endothelial cells and leukocytes. These autocrine and paracrine activation processes make platelets an important target for attenuating inflammation. The growing interest and recent discoveries in platelet biology has lead to the search for therapeutic platelet targets. Recently, platelets, although anucleate, were discovered to possess the transcription factor PPARgamma. Treatment with eicosanoid and synthetic PPARgamma ligands blunts platelet release of the bioactive mediators, soluble (s) CD40L and TXA2, in thrombin-activated platelets. PPARgamma ligand treatment may prove useful for dampening unwanted platelet activation and chronic inflammatory diseases such as cardiovascular disease.

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.

Soluble CD40L in patients with morbid obesity: significant reduction after bariatric surgery

BACKGROUND

Morbid obesity is associated with increased cardiovascular morbidity and mortality. Recent studies suggest that soluble CD40 Ligand (sCD40L) may play a pathogenetic role in atherothrombotic complications in cardiovascular disease as well as in inflammation and thrombosis. As morbid obesity is closely associated with chronic inflammation and insulin resistance (IR), it was of interest to study sCD40L in patients with morbid obesity before and after massive weight loss induced by bariatric surgery.

PATIENTS AND METHODS

A total of 34 patients (mean age 40 +/- 12 years) with morbid obesity were studied before and 27.2 months after bariatric surgery. High sensitivity assays were used to measure concentrations of fasting sCD40L, monocyte-chemoattractant-protein-1 (MCP-1) and high-sensitive C-reactive protein (hsCRP). To investigate the associations of concentration changes of the parameters studied, differences between pre- and post-operative data were assessed and tested by univariate and multivariate linear regression analysis.

RESULTS

After a mean weight loss of 33.1 +/- 18.4 kg, circulating sCD40L decreased significantly from (3.7 +/- 1.5) ng mL(-1) to (2.2 +/- 0.7) ng mL(-1), (P < 0.001). The decline in sCD40L after weight loss correlated significantly with the decrease in fasting insulin, 2-h insulin, HOMA insulin resistance (HOMA-IR), triglycerides, and the inflammatory biomarkers MCP-1 and hsCRP.

CONCLUSIONS

We have shown a marked decrease in circulating sCD40L in association with an improvement of both insulin resistance and chronic inflammation in morbidly obese patients after bariatric surgery. As high sCD40L was shown to predict cardiovascular death and myocardial infarction in several prospective studies, the observed marked lowering of sCD40L might be of clinical relevance in morbidly obese patients.

Platelets as a Novel Target for PPAR?? Ligands

Peroxisome proliferator-activated receptor gamma (PPARgamma) is an important transcription factor for lipid and glucose metabolism. Currently, the PPARgamma ligands rosiglitazone and pioglitazone are used for the treatment of type 2 diabetes mellitus because they are potent insulin sensitizers. Recently, PPARgamma has emerged as an important anti-inflammatory factor. Platelets, anucleate cells involved in hemostasis, have also been implicated as key contributors to inflammation, because they produce many pro-inflammatory and pro-atherogenic mediators when activated. Surprisingly, it was discovered recently that platelets contain PPARgamma and that PPARgamma ligands, both natural and synthetic, inhibit platelet activation and release of bioactive mediators. In particular, release of soluble CD40 ligand (sCD40L) and thromboxane (TXA(2)) was inhibited by PPARgamma ligands in thrombin-activated platelets. CD40L signaling induces pro-inflammatory processes in many cell types, and increased blood levels of sCD40L are closely associated with inflammation, diabetes, and cardiovascular disease. Targeting platelet PPARgamma will, therefore, be an important treatment strategy for the attenuation of chronic inflammatory processes and prevention of thrombus formation.