Altered plasma free carnitine response to exercise in type 1 diabetic subjects

The plasma carnitine response to prolonged exercise in 12 postprandial insulin-dependent diabetics was compared with that of eight normal controls. The diabetics reduced their morning dose of intermediate acting insulin and regular insulin to two-thirds and one-half, respectively. Insulin was injected subcutaneously into the abdominal wall. Exercise was performed on a treadmill for 90 min at 60% VO2 max. Respiratory exchange ratios (RER) decreased significantly (p less than 0.0001) during exercise in both the control and diabetic group. However, RER values were higher (p less than 0.05) in the diabetic group during most of the exercise period, corresponding to a significantly (p less than 0.05) lower proportion of the energy utilized from the oxidation of fat. In the diabetic group, mean plasma glucose at rest was 278 +/- 26 mg/dl, and decreased significantly (p less than 0.01) to 107 +/- 12 mg/dl after 90 min of exercise. In the control group, mean resting plasma glucose was 78 +/- 6 mg/dl, and dropped (p less than 0.05) to 67 +/- 3 mg/dl at 30 min of exercise. Thereafter, it showed no change. Mean resting plasma free insulin in the control group was lower compared to the diabetic group (10.2 +/- 2.0 vs 23.5 +/- 2.0 microU/ml, p less than 0.001). During exercise, insulin levels decreased significantly (p less than 0.01) in the control group while there was no change in the diabetic group. In both control and diabetic groups, percent basal total carnitine increased significantly (p less than 0.01) throughout exercise.(ABSTRACT TRUNCATED AT 250 WORDS)