Giuliana Stel

Hyperglycemia-Induced Thrombin Formation in Diabetes: The Possible Role of Oxidative Stress

Diabetes is characterized by the existence of a thrombosis-prone condition, possibly related to hyperglycemia. However, the mechanism linking hyperglycemia to the activation of the coagulation cascade is still unclear. It has been recently suggested that diabetes is accompanied by increased oxidative stress. In this work, the possibility that oxidative stress may be involved in the hyperglycemia-induced coagulation activation has been evaluated. Prothrombin fragment 1 + 2 (F1+2), which represents a reliable marker of the amount of thrombin released in the circulation, has been chosen for studying thrombin formation in vivo. In nine type II diabetic patients and in seven healthy control subjects, matched for age and body mass index, three different experiments were performed: oral glucose tolerance test (OGTT), intravenous antioxidant glutathione (GSH) administration for 2 h, and OGTT plus intravenous GSH administration. Samples were drawn at −15 min and every 30 min from 0 to 180 min. During the OGTT, F1+2 significantly increased in both diabetic and healthy subjects. GSH administration during OGTT normalized this phenomenon. GSH administered alone significantly decreased F1+2 in diabetic patients, while no effect was observed in the normal subjects. These data suggest that hyperglycemia may induce thrombin activation, possibly inducing an oxidative stress, and that antioxidant GSH may counterbalance this effect.

Total Plasma Antioxidant Capacity Predicts Thrombosis-Prone Status in NIDDM Patients

OBJECTIVE To explore the hypothesis that a relationship exists between free radical activity and abnormalities in hemostasis in NIDDM. RESEARCH DESIGN AND METHODS The use of the total radical-trapping antioxidant parameter (TRAP) has very recently been proposed to explore the antioxidant property of a plasma and their mutual cooperation. In the present study, TRAP, vitamin E, vitamin C, vitamin A, uric acid, protein-bound SH (thiol) groups, fibrinogen, prothrombin fragments F1 + 2, and D-dimer have been evaluated in 46 NIDDM patients and 47 healthy matched control subjects. RESULTS In NIDDM patients, TRAP, vitamin A, SH groups, and uric acid were significantly reduced, whereas the level of vitamin E was significantly increased. Vitamin C was similar in the two groups. Fibrinogen, prothrombin fragment 1 + 2, and D-dimer were increased in diabetic patients. TRAP, but no single other antioxidant, had a strong inverse association with fibrinogen, prothrombin fragment 1 + 2, and D-dimer. CONCLUSIONS These findings are consistent with the hypothesis that oxidative stress may condition coagulation activation in diabetics. However, the data suggest that it is the total antioxidant capacity rather than any single plasma antioxidant that is the most relevant parameter.

Effects of third-generation oral contraceptives on high-sensitivity C-reactive protein and homocysteine in young women.

OBJECTIVE: To evaluate the effect of third-generation oral contraceptives on high-sensitivity C-reactive protein (CRP), homocysteine, and lipids levels in a population of young, fertile, nonobese women. METHODS: Blood markers were evaluated in 277 healthy white women (mean age 23 years and mean body-mass index 21 kg/m2). Seventy-seven oral contraceptive users were compared with 200 non–oral contraceptive users. Progressive cutoffs of high-sensitivity CRP and homocysteine levels were examined. RESULTS: Levels of high-sensitivity CRP posing a high risk of cardiovascular disease (3.0 to less than 10.0 mg/L) were found in 27.3% of oral contraceptive users and in 8.5% of non–oral contraceptive users (odds ratio 4.04; 95% confidence interval [CI] 1.99–8.18). Levels of high-sensitivity CRP at intermediate risk (1.0 to less than 3.0 mg/L) were found in 32.5% of oral contraceptive users and in 11.0% of non–oral contraceptive users (odds ratio 3.89; 95% CI 2.03–7.46). Notably, non–oral contraceptive users were 8.65 (95% CI 4.39–17.1) times as likely to demonstrate a protective level of high-sensitivity CRP (less than 0.5 mg/L) compared with oral contraceptive users. Oral contraceptive use increased serum triglycerides (P<.001) and total cholesterol P=.001); however, high-density lipoprotein, not low-density lipoprotein, contributed to this increase. A decreased ratio of low-density lipoprotein to high-density lipoprotein cholesterol was observed in oral contraceptive users compared with nonusers (P=.016). Oral contraceptive use did not affect homocysteine levels. CONCLUSION: Third-generation oral contraceptive use increases low-grade inflammatory status measured by high-sensitivity CRP concentrations. Alteration of inflammatory status in oral contraceptive users could affect the risk of venous thromboembolism, cardiovascular disease, and other oral contraceptive-associated adverse conditions in young women. LEVEL OF EVIDENCE: II

A new model of human aortic endothelial cells in vitro.

Vascular endothelial cells play an important role in coagulation regulation of vascular tone and in a variety of synthetic and metabolic functions. Endothelial cells also have a pivotal role in immunological diseases atherogenesis and tumor angiogenesis. Endothelial cells are often used as system to study the pathophysiology of late complications in diabetes mellitus atherosclerotic damages and leukocyte adhesion in inflammatory diseases. Most of the studies have been performed on primary arterial and venous endothelial cell cultures with problems such as availability of autoptic material and reproducibility of cell cultures. We have isolated and characterized a novel system of proliferating long-term cultures of human aortic endothelial cells that maintain their differentiated characteristics for many generations in vitro. They produce antithrombotic and thrombotic factors such as t-PA and PAI-1 and respond to TNFalpha, an important factor correlated with the inflammatory process by modifying growth characteristics by producing cytokines such as GM-CSF by expressing ICAM-1 on the surface and by producing large amounts of nitric oxide and endothelin. This new system may be very useful to understand and study the molecular mechanisms involved in many vascular alteration pathologies and in the aging process.

Accuracy of a portable glucose meter and of a Continuous Glucose Monitoring device used at home by patients with type 1 diabetes

BACKGROUND Patients with diabetes are recommended to self-monitor their blood glucose levels also at home. Accuracy of a hand-held glucometer and a Continuous Glucose Monitoring (CGM) device were comparatively evaluated. METHODS Venous blood samples (for reference laboratory determinations; n=428) were collected from 18 type 1 patients (35-65 years old), immediately followed by capillary measurement (Bayer ContourLink meter) and CGM readings (Medtronic Paradigm). RESULTS Laboratory values did not differ statistically from ContourLink and CGM readings, mean difference (±SD) being -0.05±1.06 mmol/L and 0.10±1.84 mmol/L glucose, respectively. A bias ((value-reference)/reference×100) ≥15% was observed in 27.7% and 54.9% of cases, respectively. Notably, below 3.9 mmol/L glucose (hypoglycemic threshold), an absolute error>0.8 mmol/L was found in 78.9% and 94.1% of cases. The absolute errors of the CGM device were inversely related to the rate of glucose change (r=0.598, p<0.001). CONCLUSIONS A very large error was observed at the extreme glycemic values, which may lead to erroneous therapy. Consequently, performance of future portable glucometers should be focused in particular under hypo- and hyper-glycemia. Moreover, integrated CGM devices should not disregard the effect of the rate of blood glucose change on the sensor readings.

Prolonged Exercise in Type 1 Diabetes: Performance of a Customizable Algorithm to Estimate the Carbohydrate Supplements to Minimize Glycemic Imbalances

Physical activity in patients with type 1 diabetes (T1DM) is hindered because of the high risk of glycemic imbalances. A recently proposed algorithm (named Ecres) estimates well enough the supplemental carbohydrates for exercises lasting one hour, but its performance for prolonged exercise requires validation. Nine T1DM patients (5M/4F; 35–65 years; HbA1c 54±13 mmol·mol-1) performed, under free-life conditions, a 3-h walk at 30% heart rate reserve while insulin concentrations, whole-body carbohydrate oxidation rates (determined by indirect calorimetry) and supplemental carbohydrates (93% sucrose), together with glycemia, were measured every 30 min. Data were subsequently compared with the corresponding values estimated by the algorithm. No significant difference was found between the estimated insulin concentrations and the laboratory-measured values (p = NS). Carbohydrates oxidation rate decreased significantly with time (from 0.84±0.31 to 0.53±0.24 g·min-1, respectively; p<0.001), being estimated well enough by the algorithm (p = NS). Estimated carbohydrates requirements were practically equal to the corresponding measured values (p = NS), the difference between the two quantities amounting to –1.0±6.1 g, independent of the elapsed exercise time (time effect, p = NS). Results confirm that Ecres provides a satisfactory estimate of the carbohydrates required to avoid glycemic imbalances during moderate intensity aerobic physical activity, opening the prospect of an intriguing method that could liberate patients from the fear of exercise-induced hypoglycemia.

Effect of intensive glycaemic control on fibrinogen plasma concentrations in patients with Type II diabetes mellitus. Relation with β-fibrinogen genotype

Summary Recent studies show that in diabetic subjects an increase of plasma fibrinogen concentration is associated with a high risk of cardiovascular complications. Environmental and genetic factors contribute to the plasma fibrinogen concentration. Several studies indicate a relation between the polymorphism in the 5 ′ region of the β-fibrinogen gene and plasma protein concentrations and in diabetes the possible influence of hyperglycaemia on fibrinogen is still debated. In this study we investigated these relations. Hind III polymorphism was evaluated by a polymerase chain reaction-technique. On the basis of the observed allelic combination of fibrinogen β-gene polymorphism and the existence of poor metabolic control (glycated haemoglobin ≥ 7.5 %), 50 Type II diabetic patients were selected. They were divided into three groups according to their β-gene polymorphism (α1α1: n = 20, α1α2: n = 15, α2α2: n = 15) and then intensive insulin therapy was started. After 3 months of intensive treatment, the improvement in glycaemic control was equivalent, in terms of glycated haemoglobin, in all the three groups. A fibrinogen reduction was observed in α1α2 and α2α2 but not in α1α1 subjects. These results underline a possible relation between fibrinogen genotypes and glycaemic control in determining plasma fibrinogen concentrations in diabetic patients. [Diabetologia (1998) 41: 1270–1273]

Retinol binding protein as early marker of fetal growth restriction in first trimester maternal serum.

Abstract Background: Serum retinol binding protein (RBP4) is the binding protein for retinol, being delivered into the circulation through the carrier protein transthyretin (TTR) together with thyroxin (T4). RBP4 has also been recently indicated as a new adipokine implicated in insulin resistance and metabolism regulation. Objective: To investigate the role of RBP4 as early markers of fetal growth restriction (FGR) and preeclampsia (PE) in maternal serum during the first trimester of pregnancy. Materials and methods: Retrospective case control study in patients between the 12th and the 14th week of gestation. RBP4, TTR and T4 concentration was assessed in maternal serum of three groups of women: 15 and 14 patients later developing respectively FGR and PE were compared with 11 patients having a normal pregnancy. Results: All women were Caucasian and the mean maternal age was 33.62 years (±5.50). RBP4 resulted lower in the FGR than in the control group (11.00 versus 16.00 µg/ml, p < 0.05) and than in the PE group (15.00 µg/ml, p = 0.075), both in bivariate and multivariate analysis. No difference was observed in TTR and T4 concentration. Conclusions: RBP4 seems to play a role as early marker of FGR but not PE in first trimester maternal serum.