Effect of insulin on von Willebrand factor release in normal and diabetic subjects: in vivo and in vitro studies

Concanavalin A, but not glycated albumin, increases subendothelial deposition of von Willebrand factor in vitro

Diabetes is associated with augmentation of prothrombogenic von Willebrand factor (vWF) content in plasma. Earlier, the author and colleagues have shown that high glucose and insulin do not appreciably influence deposition of vWF into the subendothelial extracellular matrix (SECM) produced by cultured human umbilical vein endothelial cells (HUVECs). In the present work, the author used this model to test the effects of nonenzymatically glycated albumin (Glyc-HSA) and two lectins, concanavalin A (ConA) and wheat germ agglutinin (WGA), on vWF deposition into the SECM. First-passage HUVECs were seeded into gelatin-coated 96-well plates and cultured for 6 to 7 days. HSA or Glyc-HSA (at concentrations 25, 50, and 100 microg/mL), and WGA or ConA (4, 8, and 16 microg/mL) were added 3 h after seeding. Cell viability was tested by the MTT method. To determine vWF contents in the SECM, HUVECs were detached by treatment with NH4OH and the residual material was used as a solid phase in an enzyme-linked immunosorbent assay (ELISA)-like assay with primary (anti-vWF) and secondary (peroxidase-conjugated) antibodies. Addition of Glyc-HSA did not essentially influence VWF contents in the SECM (A490 was 0.226 versus 0.268 at 0 and 100 microg/mL, respectively; p > .05, n = 16). Cultivation in the presence of WGA led to the deterioration of cell viability, which was accompanied by a significant decrease of vWF in the SECM (0.248 versus 0.128 at 0 and 16 microg/mL, respectively; p < .001, n = 16). ConA did not influence viability of HUVECs, but this lectin at all concentrations consistently increased the deposition of vWF (up to 164% relative to control, p <.001; n = 16). These data indicate that endothelial carbohydrate determinants and corresponding ligands (namely, mannose-specific lectins) may be involved in the regulation of production and deposition of vWF.

Using insulin as a drug rather than as a replacement hormone during acute illness: a new paradigm

The direct correlation between glucose levels and cardiovascular disease in individuals with type 2 diabetes can now be applied to individuals that share an abnormal metabolic milieu similar to that found in central obesity, the metabolic syndrome, and type 2 diabetes. Premature macrovascular complications with a very high morbidity and mortality rate can be found in these nondiabetic populations. The typical phenotype has visceral or central obesity, excess of free fatty acids, insulin resistance, increased insulin secretion, and hypertension. A more complex metabolic-cardiovascular syndrome develops that includes dyslipidemia, abnormal production of cytokines, chronic inflammatory state, and abnormal coagulation. The interplay of all these cardiovascular risk factors is responsible for the accelerated atherosclerotic process. The different terminologies used for populations sharing this common ground for premature cardiovascular disease now generally accepted as the metabolic syndrome, are also discussed. Aggressive insulin treatment during acute illness in individuals with the abnormal metabolic milieu is beneficial. Insulin treatment is changing from using insulin as a hormone to treat only severe hyperglycemia, to a new paradigm using insulin in high doses as a drug. Aggressive insulin regimens should be used to treat only minimal elevations of blood glucose or to prevent hyperglycemia. The newly observed properties of insulin are reviewed which include suppression of inflammatory cytokines and adhesion molecules, improved hemostasis, and other cardiac beneficial effects. The concomitant administration of intravenous glucose and insulin permits the administration of higher insulin doses that can result in improved outcome due to its nonglycemic-related benefits. The use of aggressive insulin therapy requires both better and more cost-effective algorithms to successfully treat this high-risk population during acute illness.

Diabetic ketoacidosis promotes a prothrombotic state

Cerebrovascular accidents are one of the life-threatening complications of diabetic ketoacidosis (DKA) in children and adolescents. Our objective was to evaluate the effect of DKA and its treatment on factors known to affect thrombotic activity (protein C; protein S; von Willebrand factor, fibrinogen; homocysteine; and folate) by comparing seven adolescents with DKA prior to treatment and at 6, 24, and 120 hours after initiation of treatment. We found that protein C activity was significantly decreased by DKA, but normalized slowly following treatment. Free protein S was low throughout the study. Protein C antigen and protein S antigen showed varying degrees ofchange within the first 24 hours, but remained in the normal range, with the exception of the initial value of protein C antigen, which was elevated. von Willebrand factor (vWF) antigen and vWF activity were both significantly increased prior to treatment, but decreased with treatment. However, vWF activity remained elevated at 120 hours. Fibrinogen concentrations showed no significant changes throughout the study. Homocysteine was significantly decreased prior to treatment and increased with the initiation of treatment Folate was significantly increased prior to treatment, and decreased to high normal levels. The increased vWF and the decreased levels of protein C activity and of free protein S support the hypothesis that DKA and its treatment results in a prothrombotic state and activation of the vascular endothelium, which, in turn, predispose to cerebrovascular accidents.