Stimulation of prostacyclin synthesis by physical exercise in type I diabetes

We examined the effect of short- and long-term exercise on prostacyclin (prostaglandin I2 [PGI2]) and thromboxane A2 (TXA2) synthesis in type I (insulin-dependent) diabetic patients and healthy control subjects. PGI2 synthesis was assessed by determining the urinary excretion of 6-keto-PGF1 alpha and 2,3-dinor-6-keto-PGF1 alpha and TX synthesis by measuring TXB2 in serum and urine. In the resting state, prostanoid excretion and concentrations were similar in diabetic and control subjects. During 40 min of ergometric cycling exercise, the urinary excretion of 6-keto-PGF1 alpha (a hydration product of vasodilatory PGI2) increased 5.8-fold more in the 12 control subjects than in the 15 diabetic patients (P less than .02). Serum TXB2 concentration rose similarly in diabetic patients and control subjects (P less than .05). During a 75-km competitive cross-country ski race (7 h, 30 min), urinary excretion of 6-keto-PGF1 alpha rose 1.9-fold in 7 diabetic (P less than .05) and 3.3-fold in 10 control (P less than .001) subjects, whereas urinary dinor excretion, reflecting vascular PGI2 synthesis more closely, increased only in the control subjects (P less than .01). Urinary TXB2 excretion remained unchanged in both groups during long-term exercise. These data suggest that diabetic patients have normal PGI2 and TXA2 synthesis in the resting state but diminished PGI2 response to both acute and prolonged exercise.