Endurance exercise has been advocated in diabetes mellitus to improve both metabolic control and prevent atherosclerotic complications. The response of the fibrinolytic system during prolonged exercise has not been studied in diabetes.
In seven male marathon runners with IDDM and eight healthy nondiabetic male control subjects, matched for age and degree of training, we studied fibrinolytic and coagulation parameters during a 3-h 32-km outdoor running session. Measurements included t-PA, u-PA, PAI-1, PAP (as a measure of in vivo activation of fibrinolysis), FbDPs, FGN, vWF, and VIII:C.
In both IDDM and control subjects, levels of t-PA, u-PA, PAP, vWF, and VIII:C continued to rise throughout the exercise, whereas PAI-1 showed a similar decline in both groups. FbDP rose slightly in both groups, and FGN remained unchanged. t-PA levels during exercise correlated closely with exercise intensity. These findings indicate that continued stimulation by exercise does not deplete endothelial PA stores. Differences between IDDM and control subjects were seen only for t-PA, vWF, and u-PA. The AUC during exercise (AUC0.5−3.0) of t-PA in IDDM was insignificantly lower than in control subjects (53 ± 19 vs. 67 ± 31 ng.ml−1.h), but the ratio of t-PA to exercise intensity was lower in IDDM (0.24 ± 0.11 vs. 0.31 ± 0.13, P < 0.05). The AUC0.5−3.0 of vWF was lower in IDDM than in control subjects (569 ± 268 vs. 880 ± 265%·h, P < 0.05). The AUC0.5−3.0 of u-PA was higher in IDDM than in control subjects (15.1 ± 3.5 vs. 11.2 ± 1.8 ng.ml−1.h, P < 0.05).
Despite a defect in the exercise-induced endothelial release of vWF and t-PA, the overall potential to activate fibrinolysis is intact in IDDM, possibly by enhancement of u-PA after exercise. Our data suggest that in IDDM, as in nondiabetic subjects, long-distance running may slow the progression of atherosclerosis by stimulating fibrinolysis.
