Acute hyperglycemia impairs platelet receptor expression but not platelet aggregation in vitro

Introduction

Elevated blood glucose concentration is an important factor for mortality and morbidity in critically ill patients. Previously, a randomized controlled trial showed that a blood glucose level of about 6 mmol/l is associated with less multiorgan failure and a significantly higher survival rate compared with levels above 8 mmol/l. Platelets play a crucial role in hemostasis and inflammation. However, the effect of short-term elevated blood glucose levels on platelet activation has not yet been evaluated systematically.

Objective

To evaluate the influence of blood glucose levels on platelets in vitro.

Methods

Citrated blood samples were drawn from healthy blood donors (40% male, age 38 ± 13 years [mean ± SD]). Exclusion criteria were smoking and the use of drugs interfering with platelet function. Blood samples were adjusted with glucose (Sigma, Taufkirchen, Germany) to final concentrations of 5 mmol/l (control group), 10 mmol/l (group 1) and 15 mmol/l (group 2), respectively. Samples were incubated for 10 min at 37°C with fluorescence-labeled monoclonal antibodies against CD62P, CD41, CD36, or CD42b (all: Beckman-Coulter, Krefeld, Germany). To evaluate platelet reactivity 2 and 6 μM thrombin-receptor-agonist-peptide-6 (TRAP-6; Bachem, Heidelberg, Germany) or 5 and 10 μM adenosine-di-phosphate (ADP; Sigma, Taufkirchen, Germany) were added. Analyses were performed in a flow-cytometer (EpicsXL; Beckman-Coulter). The mean fluorescence intensity was calculated. Determination of platelet aggregation was performed by the turbidimetric procedure (BCT, Dade Behring, Marburg, Germany). Aggregation was induced with ADP (200 μM/l), collagen (2 mg/l) and epinephrine (100 μM/l; all Dade Behring). Statistics for intergroup differences were performed by one-way ANOVA.

Results

The initial blood glucose concentration was 5.0 ± 1.1 mmol/l. The blood glucose level had no significant influence on the expression of CD36 and CD62P, with and without stimulation. By contrast we observed a significant decrease in expression of CD42b in group 2 compared with the control group (unstimulated, P < 0.001; TRAP-6, P = 0.005; ADP, P = 0.012). A similar observation was made for CD41 expression (unstimulated, P < 0.001; TRAP-6, P < 0.05; ADP, P < 0.001). Also in group 1, a significant decrease in CD41 expression was observed after ADP stimulation. No significant differences were seen by aggregometry with either agonist.

Conclusion

This in vitro study demonstrates that elevated blood glucose levels reduce expression of platelet receptors CD41 and CD42b. In contrast, platelet function measured by aggregometry showed no impairment. We conclude that acute hyperglycemia does not lead to lowered platelet function.