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(Circulation. 2003;108:2653.)
© 2003 American Heart Association, Inc.

Clinical Investigation and Reports

Effects of Intense and Prolonged Exercise on Insulin Sensitivity and Glycogen Metabolism in Hypertensive Subjects

Caroline Rhéaume, MSc; Paulo-Henrique Waib, MD, PhD; N’Guessan Kouamé, PhD; André Nadeau, MD; Yves Lacourcière, MD; Denis R. Joanisse, PhD; Jean-Aimé Simoneau, PhD; Jean Cléroux, PhD

From the Hypertension (C.R., P.-H.W., N.K., Y.L., J.C.) and Diabetes (A.N.) Research Units, Laval University Hospital Research Center, and the Kinesiology Division, Laval University (D.R.J., J.-A.S.), Québec, Canada.

Correspondence to Jean Cléroux, PhD, HDQ Research Center, 9, rue McMahon, Québec, Québec, Canada G1R 2J6. E-mail jean.cleroux{at}crhdq.ulaval.ca

Received October 17, 2002; de novo received April 4, 2003; revision received August 14, 2003; accepted August 17, 2003.

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.

Methods and 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 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.

Key Words: exercise • insulin • glycogen • hypertension

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