Carbohydrate and lipid metabolism in type I diabetics during exhaustive exercise

During an exhaustive graded bicycle spiroergometer test, several arterial blood samples were taken from six type I diabetics and seven normal controls for determination of catecholamines and parameters of carbohydrate and lipid metabolism. In both groups during exercise, glucose remained unchanged, and lactate associated metabolic acidosis was compensated by respiratory gas exchange. Diabetics showed an impaired exercise-induced response of adrenaline and noradrenaline (62 +/- 8 to 176 +/- 24 and 98 +/- 6 to 612 +/- 175 pg X ml-1), respectively, compared to controls (55 +/- 6 to 1213 +/- 720 and 95 +/- 17 to 1710 +/- 506 pg X ml-1). Free glycerol increased to an equivalent extent in both groups. Simultaneously produced free fatty acids decreased at high work loads in diabetics. In addition to insulin deficiency and impaired catecholamine secretion, diabetics showed high values of growth hormone, ACTH, and cortisol. These may be responsible for the high values of free glycerol and free fatty acids. At maximum the FFA values decreased in both groups, although levels of lactate and pyruvate were high. It is suggested that insulin deficiency is the reason for the disturbed hormonal and metabolic response to exhaustive exercise and reduces physical fitness in diabetics.