Increased thromboplastic potential in diabetes: a multifactorial phenomenon

Diabetes mellitus and risk of venous thromboembolism

BACKGROUND

: To determine if diabetes mellitus is a risk factor for venous thromboembolism (VTE).

RESEARCH DESIGN AND METHODS

: Data from the National Hospital Discharge Survey were analyzed from 1979 to 2005. International Classification of Diseases, Ninth Revision, Clinical Modification codes were used to identify diseases.

RESULTS

: Among 92,240,000 patients with diabetes mellitus discharged between 1979 and 2005, 1,267,000 (1.4%) had VTE. The relative risk for VTE was elevated only in patients younger than 50 to 59 years and was highest in patients aged 20 to 29 years (relative risk = 1.73). Relative risks of VTE with uncomplicated type 1 diabetes mellitus and uncomplicated type 2 diabetes mellitus were similar and also age dependent. In patients with uncomplicated diabetes mellitus who did not have obesity, stroke, heart failure, or cancer, compared with those who did not have diabetes mellitus and did not have any of these comorbid conditions, the relative risk for VTE was 1.52 in patients aged 20 to 29 years and 1.19 in patients aged 30 to 39 years. In older patients, the relative risk of VTE in patients with diabetes mellitus was not increased.

CONCLUSIONS

: Diabetes mellitus carries an increased risk for VTE, which is apparent only in younger patients in whom comorbid conditions that also increase the risk of VTE are unlikely to be present.

Acute hyperglycemia increases soluble P-selectin in male patients with mild diabetes mellitus

The aim of this study was to examine if acute hyperglycemia (an oral glucose tolerance test) activates platelet function, endothelial cells or thrombin generation in diabetic patients and healthy controls. Eleven males with mild type II diabetes mellitus and 11 healthy male volunteers, matched for age and body mass index, were investigated before and after the glucose load. Soluble P-selectin, von Willebrand factor antigen and markers of thrombin generation in plasma were determined by immunoassays, and platelet P-selectin expression (unstimulated and agonist-stimulated) by flow cytometry in whole blood. Acute hyperglycemia elevated plasma soluble P-selectin from 32.5 to 50.9 ng/ml in the diabetic group (P = 0.05) but not in the controls (from 27.3 to 28.8 ng/ml; P = 0.6). Also, soluble P-selectin levels were higher in patients with diabetes than in healthy controls during hyperglycemia, but not in the fasting state. Adenosine diphosphate- and thrombin-induced platelet P-selectin expression was slightly, but significantly, decreased by the glucose load, whereas platelet P-selectin expression in unstimulated samples was not affected. Plasma levels of von Willebrand factor and thrombin generation were similar in patients and controls, and were not altered by hyperglycemia. In conclusion, we found that acute hyperglycemia elevates soluble P-selectin in plasma in males with mild type II diabetes mellitus. Our observation of unaltered plasma levels of the endothelial marker von Willebrand factor is in agreement with platelets being the main source of P-selectin released into plasma following hyperglycemia. Thus, platelets in individuals with type II diabetes may be more susceptible to hyperglycemia than platelets in non-diabetic individuals.

Plasminogen in proliferative vitreoretinal disorders

OBJECTIVE

Intravitreal fibrin formation is a frequent observation after vitrectomy performed for a variety of vitreoretinal disorders including proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR), and endophthalmitis. Plasminogen activators (PA) have been used for the management of this postoperative complication. This approach requires the presence of plasminogen, the substrate for PA mediated fibrinolysis, in the vitreal cavity.

METHODS

Quantification of plasminogen in the vitreous of 60 patients with PVR, PDR, and macular pucker was performed by streptokinase mediated activation using a chromogenic substrate. The presence of immunoreactive plasminogen was confirmed by immunoblot analysis of vitreal proteins and immunocytochemistry of surgically removed epiretinal membranes.

RESULTS

Plasminogen levels were dramatically increased in the vitreous of PVR and PDR patients compared with macular pucker patients and normal controls. Staining for plasminogen in epiretinal membranes was confined to the extracellular matrix. Predominant staining of perivascular areas in PDR specimens indicated that breakdown of the blood-retinal barrier is an important source of intravitreal plasminogen in that condition.

CONCLUSION

Plasminogen may play a role in traction membrane formation in PVR and PDR. Our biochemical analysis of presurgical vitreous indicates that there may be abundant substrate for PA mediated fibrinolysis in the vitreous cavity after vitrectomy.

Adhesion molecules influencing atherosclerosis

Life limiting diabetes heart problems predominantly result from accelerated thrombogenesis superimposed on a localized arterial vessel stenosis (atherothrombosis). The atherosclerotic process is a slowly progressing vitious cycle of self-amplifying cell-cell interactions. Initially, corpuscular blood elements, predominantly monocytes adhere to locally activated endothelial cells, before they convert into lipid laden macrophages. The proliferative response of media smooth muscle cells to foam cell derived mediators proceeds to the fibrous plaque where underlying subendothelial matrix material activates bypassing platelets. The new concept of adhesion molecules explains how streaming white blood cells can locally adhere to the endothelial cells (selectin mediated), become triggered, stick (integrin mediated) and consecutively transmigrate. P-Selectin rapidly appears in the outer membrane of activated endothelial cells and platelets. It serves as receptor for sialic acid containing oligosaccharides within the monocyte/PMN membrane. These cells adhere to locally activated endothelium (nondenuding injury) and form nidus for the further adherence of activated platelets. Later, when platelets become activated in response to nuding endothelial injury, exposure of P-Selectin leads to the parallel local recruitment of white blood cells. Diabetic patients with clinically overt angiopathy, but also immediately after onset of the metabolic disease, were shown to have increased levels of circulating P-Selectin positive platelets. Therefore, it is suggested that enhanced platelet-leukocyte interaction might be pathogenetic for atherogenesis from the very beginning as it must be considered of importance for reperfusion injury and remodelling in a highly affected myocardium when the catastrophe of myocardial infarction has finally occurred.

Patterns of contact phase proteins indicating neuropathy in diabetic patients

In 42 outpatients of the diabetology division, coagulation and fibrinolysis variables were determined in order to detect typical patterns of results with which it was possible to discriminate between three groups with different diabetic complications (17: no complication, 7: angiopathy alone, 18: neuropathy with or without other complications). There was a statistically significant discriminatory function involving C1-inhibitor concentration, high molecular weight kininogen coagulant activity and fibrinogen as the most decisive variables. The neuropathy group was appropriately separated from the others with an 81% correct reclassification. Heparin cofactor II, histidine-rich glycoprotein, alpha 2-macroglobulin, pre-kallikrein and factor XII had no discriminative power.

Role of sodium in protection by extended-spectrum penicillins against tobramycin-induced nephrotoxicity

Salt depletion is known to potentiate aminoglycoside nephrotoxicity, while salt replacement attenuates it. Recent studies have shown that ticarcillin protects against tobramycin and gentamicin nephrotoxicity. It has been suggested that this protection is due to an interaction between ticarcillin and the aminoglycoside. However, it can also be explained by the salt load associated with ticarcillin administration. This study was conducted to examine this question. Tobramycin was administered to eight groups of rats at 100 mg/kg per day intraperitoneally for 10 days. Group 1 rats were salt depleted, while group 2 rats were on a normal salt diet. Rats in groups 3 through 8 were also salt depleted but received, in addition, the following interventions intraperitoneally: group 3, ticarcillin, 300 mg/kg per day (0.37 to 0.39 meq of Na supplement per day); group 4, ticarcillin, 300 mg per day (1.56 meq of Na supplement per day); group 5, ticarcillin, 300 mg/kg per day, and NaCl supplement (1.17 to 1.19 meq/day), resulting in a total load of 1.56 meq/day; group 6, piperacillin, 400 mg/day (0.76 meq of Na supplement per day and equimolar to the ticarcillin dose [300 mg/day] in group 4 rats); group 7, piperacillin, 400 mg/day, and NaCl supplement (0.8 meq/day) for a total Na load of 1.56 meq/day; and group 8, 1.56 meq of Na per day as NaCl. Rats in groups 2, 4, 5, 7, and 8, which received a normal salt diet or its equivalent Na supplement, had no significant change in creatinine clearance (CLCR) over the 10-day period. The remaining groups sustained significant reductions in CLCR, as follows: group 1, -53.0% (P < 0.05); group 3, -66.2% (P < 0.05); group 6, -79.8% (P < 0.05). A positive correlation was found between the concentration of tobramycin in the kidneys and the percent change in CLCR at the end of the study. Concentrations of drugs in plasma were highest in group 1 rats, lowest in the rats in groups in which protection was observed, and moderately elevated in the remaining groups of rats. The results of this study suggest the following: (i) that the protective effect of ticarcillin against tobramycin nephrotoxicity is secondary to the obligatory sodium load associated with it, (ii) pharmacokinetic and pharmacodynamic interactions between salt and tobramycin are proposed to explain this effect, (iii) the nephrotoxicity of tobramycin is probably related to the degree of accumulation of the drug in the kidney, and (iv) an in vivo interaction between tobramycin and ticarcillin does not contribute to the protective effect of the penicillin but may influence concentrations in plasma, especially under conditions of severe renal impairment.