Exercise shifts the platelet aggregation modulatory role from native to mildly oxidized low-density lipoprotein

Purpose: The role of low-density lipoprotein (LDL) lipid peroxides in stren uous exercise-induced changes in platelet function was studied in 30 patien ts (male/female = 22/8) aged 30-62 yr (mean +/- SD = 508). Methods: All sub jects were subjected to a Treadmill exercise test, using the standard Brace protocol. Blood samples were collected pre-, peak, and 10 min postexercise to assess hematological and biochemical parameters and platelet aggregatio n. Ex vivo whole blood platelet aggregation during treadmill exercise was a ssessed in 10 subjects by adding mildly oxidized LDL. Results: Preexercise, a correlation existed between plasma thromboxane (TX) levels and plasma LD L cholesterol or beta-thromboglobulin (P-TG) levels (r = 0.48, P < 0.05; r = 0.47, P < 0.05, respectively), whereas, at peak exercise, TX and beta-TG levels increased, but no correlation was seen. At peak exercise, platelets showed hyperaggregability in terms of maximal amplitude and reaction slope (P < 0.001 and P < 0.01, respectively). In contrast to the increase in plas ma lipid peroxide levels seen during peak exercise (P < 0.05), LDL lipid pe roxides decreased during exercise, this decrease reaching a statistical sig nificance at 10 min postexercise (P < 0.05). In addition, the ex vivo addit ion of mildly oxidized LDL (10 mg protein.L-1) to peak exercise blood resul ted in a significant attenuation of platelet aggregation and a decrease in TX release. At 10 min postexercise, a correlation was seen between LDL lipi d peroxides and TX levels (r = 0.78, P < 0.001) or beta-TG levels (r = 0.68 , P < 0.005). Conclusion: These results suggest that LDL lipid peroxides pl ay a role in modulating and attenuating platelet aggregation during strenuo us exercise.