Hyperglycemia-Induced Platelet Activation in Type 2 Diabetes Is Resistant to Aspirin but Not to a Nitric Oxide-Donating Agent

OBJECTIVE - Acute, short-term hyperglycemia enhances high shear stress induced platelet activation in type 2 diabetes. Several observations suggest that platelets in type 2 diabetes are resistant to inhibition by aspirin. Our aim was to assess comparatively the effect of aspirin, a nitric oxide donating agent (NCX 4016), their combination, or placebo on platelet activation induced by acute hyperglycemia in type 2 diabetes. RESEARCH DESIGN AND METHODS - In a double-blind, placebo-controlled, randomized trial, 40 type 2 diabetic patients were allocated to 100 mg aspirin once daily, 800 mg NCX 401.6 bid., both of them, or placebo for 15 days. On day 15, 1 h after the morning dose, a 4-h hyperglycemic clamp (plasma glucose 13.9 mmol/l) was performed, and blood samples were collected before and immediately after it for platelet activation and cyclooxygenase-1 (COX-1) inhibition studies. RESULTS - Acute hyperglycemia enhanced shear stress induced platelet activation in placebo-treated patients (basal closure time 63 +/- 7.1 s, after hyperglycemia 49.5 +/- 1.4s, 13.5 +/- 6.3 s, P < 0.048). Pretreatment with aspirin, despite full inhibition of platelet COX-1., did not prevent it (-12.7 +/- 6.9 s, NS vs. placebo). On the contrary, pretreatment with the NO donor NCX 4016, alone or in combination with aspirin, suppressed platelet activation induced by acute hyperglycemia (NCX 4016 +10.5 +/- 8.3s; NCX 4016 plus aspirin: +12.0 +/- 10.7s, P < 0.05 vs. placebo for both). Other parameters of shear stress dependent platelet activation were also more inhibited by NCX 4016 than by aspirin, despite lesser inhibition of COX-1. CONCLUSIONS - Acute hyperglycemia-induced enhancement of platelet activation is resistant to aspirin; a NO-donating agent suppresses it. Therapeutic approaches aiming at a wider platelet inhibitory action than that exerted by aspirin may prove useful in patients with type 2 diabetes.