Thromboxane-dependent CD40 ligand release in type 2 diabetes mellitus

OBJECTIVES The goals of this study were to characterize the platelet contribution to Soluble CD40 ligand (sCD40L), to correlate its formation with the extent of oxidative stress and platelet activation, and to investigate the effects of improved metabolic control and low-dose aspirin on these processes. BACKGROUND Inflammation, oxidative stress, and platelet activation are involved in the pathogenesis of type 2 diabetes (T2DM) and its complications. The CD40-CD40L interactions result in inflammatory and pro-thrombotic responses. METHODS Urinary 8-iso-prostaglandin (PG)F-2 alpha and 11-dehydro-thromboxane (TX)B-2, in vivo markers of oxidative stress and platelet activation, respectively, plasma CD40L, and C-reactive protein (CRP) were measured in 114 T2DM patients and 114 control patients. A randomized, parallel group, 17-day study of aspirin (30, 100, or 325 mg/day) was performed in 18 T2DM patients. A similar study was performed in six healthy volunteers (aspirin, 100 mg/day). Twenty poorly controlled T2DM patients were studied before and after improved metabolic control. RESULTS Compared with control patients, diabetic patients showed significantly higher levels of 8-iso-PGF(2 alpha), 11-dehydro-TXB2, sCD40L, and CRP. On multiple regression analysis, 11-dehydro-TXB2 and 8-iso-PGF(2 alpha) excretion rates predicted sCD40L levels. Soluble CD40L linearly correlated with 11-dehydro-TXB2 (rho = 0.67, p < 0.0001), and both were reduced after one week of aspirin (p < 0.0026), with slow recovery over 10 days after aspirin withdrawal. Improved metabolic control was associated with a reduction in sCD40L, 8-iso-PGF(2 alpha), and 11-dehydro-TXB2. CONCLUSIONS This study provides several lines of evidence for the dependence of sCD40L release on TXA(2)-dependent platelet activation in T2DM and provides novel mechanistic insight into the amplification loops of persistent platelet activation in this setting.