Effects of intense and prolonged exercise on insulin sensitivity and glycogen metabolism in hypertensive subjects.
BACKGROUND
The information that insulin sensitivity and glycogen synthesis are reduced in hypertension arises primarily from studies using insulin infusions. Whether glycogen metabolism is actually altered in a physiological condition, such as during and after prolonged exercise, is currently unknown.


RESULTS
To examine this issue, 9 hypertensive and 11 normotensive subjects were evaluated on a rest day and after intense and prolonged exercise on a separate day. Insulin sensitivity and hemodynamic variables were measured on both days. On the exercise day, whole-body substrate utilization was assessed and muscle biopsies were taken in the leg at baseline, immediately after exercise, and 2.5 and 4 hours after exercise. Insulin sensitivity at rest was lower in hypertensive than normotensive subjects (P<0.05) and increased after exercise in normotensive (P<0.01) but not in hypertensive (P=NS) subjects. Leg blood flow increased after exercise in both groups but to a lesser extent in hypertensive than normotensive subjects. Baseline glycogen content and maximal glycogen synthase activity were higher in hypertensive than normotensive subjects (P<0.001). Glycogen concentration decreased relatively less (-35 versus -66%) and returned to baseline levels faster in hypertensive subjects after exercise. Hypertensive subjects used approximately 40% less carbohydrates during exercise (P<0.001) at the expense of greater free fatty acid oxidation.


CONCLUSIONS
It is concluded that increased intramuscular glycogen storage and resynthesis in hypertension are independent of blood flow and may represent compensatory mechanisms for the reduced insulin sensitivity and carbohydrate metabolism in this condition.
Rhéaume
Caroline
C
Hypertension, University Hospital Research Center, Québec, Canada G1R 2J6.
Waib
Paulo-Henrique
PH
Kouamé
N'Guessan
N
Nadeau
André
A
Lacourcière
Yves
Y
Joanisse
Denis R
DR
Simoneau
Jean-Aimé
JA
Cléroux
Jean
J
D000328:Adult; D001706:Biopsy; D001794:Blood Pressure / Q000502:physiology; D005951:Glucose Tolerance Test; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D007866:Leg / Q000098:blood supply; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism / Q000502:physiology; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology
D006003:Glycogen; D006006:Glycogen Synthase