TY - JOUR
T1 - Catecholamines in prevention of hypoglycemia during exercise in humans
AU - Marker, J. C.
AU - Hirsch, I. B.
AU - Smith, L. J.
AU - Parvin, C. A.
AU - Holloszy, J. O.
AU - Cryer, P. E.
PY - 1991
Y1 - 1991
N2 - To assess the role of catecholamines in the prevention of hypoglycemia during moderate exercise (~60% peak O2 consumption for 60 min), normal humans were studied with combined α- and β-adrenergic blockade and with adrenergic blockade while changes in insulin and glucagon were prevented with the islet clamp technique (somatostatin infusion with insulin and glucagon infused at fixed rates). The results were compared with those from an islet clamp alone study. In contrast to a comparison study (saline infusion), adrenergic blockade resulted in a small initial decrease in plasma glucose during exercise, from 5.0 ± 0.2 to 4.4 ± 0.2 mmol/l (P < 0.01), but the level then plateaued. There was a substantial exercise-associated decrement in plasma glucose when insulin and glucagon were held constant, i.e., from 5.5 ± 0.2 to 3.4 ± 0.2 mmol/l (P < 0.0001), but the level again plateaued. However, when insulin and glucagon were held constant and catecholamine actions were blocked simultaneously, progressive hypoglycemia, to 2.6 ± 0.3 mmol/l (P < 0.001), developed during exercise. Hypoglycemia was the result of an absent increase in glucose production and an exaggerated initial increase in glucose utilization. Thus we conclude that sympathochromaffin activation plays a minor role when insulin and glucagon are operative, but a catecholamine, probably epinephrine, becomes critical to the prevention of hypoglycemia during exercise when changes in insulin and glucagon do not occur.
AB - To assess the role of catecholamines in the prevention of hypoglycemia during moderate exercise (~60% peak O2 consumption for 60 min), normal humans were studied with combined α- and β-adrenergic blockade and with adrenergic blockade while changes in insulin and glucagon were prevented with the islet clamp technique (somatostatin infusion with insulin and glucagon infused at fixed rates). The results were compared with those from an islet clamp alone study. In contrast to a comparison study (saline infusion), adrenergic blockade resulted in a small initial decrease in plasma glucose during exercise, from 5.0 ± 0.2 to 4.4 ± 0.2 mmol/l (P < 0.01), but the level then plateaued. There was a substantial exercise-associated decrement in plasma glucose when insulin and glucagon were held constant, i.e., from 5.5 ± 0.2 to 3.4 ± 0.2 mmol/l (P < 0.0001), but the level again plateaued. However, when insulin and glucagon were held constant and catecholamine actions were blocked simultaneously, progressive hypoglycemia, to 2.6 ± 0.3 mmol/l (P < 0.001), developed during exercise. Hypoglycemia was the result of an absent increase in glucose production and an exaggerated initial increase in glucose utilization. Thus we conclude that sympathochromaffin activation plays a minor role when insulin and glucagon are operative, but a catecholamine, probably epinephrine, becomes critical to the prevention of hypoglycemia during exercise when changes in insulin and glucagon do not occur.
KW - Cycle exercise
KW - Epinephrine
KW - Glucagon
KW - Glucose counterregulation
KW - Insulin
KW - Norepinephrine
KW - Somatostatin
UR - http://www.scopus.com/inward/record.url?scp=0025730961&partnerID=8YFLogxK
U2 - 10.1152/ajpendo.1991.260.5.e705
DO - 10.1152/ajpendo.1991.260.5.e705
M3 - Article
C2 - 1674642
AN - SCOPUS:0025730961
SN - 0002-9513
VL - 260
SP - E705-E712
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 5 23-5
ER -