Habitual exercise attenuates the increase in myocardial diastolic
stiffness produced by diabetes mellitus in rats.
Woodiwiss, Angela J., William J. Kalk, and Gavin R. Norton.
Laboratory of Cardiovascular Pathophysiology, Department of
Physiology and the Department of Medicine University of the
Witwatersrand Medical School, Johannesburg, South Africa
APStracts 3:0193H, 1996.
The effects of regular, voluntary (habitual) exercise on left
ventricular (LV) diastolic performance, as well as on those
hemodynamic, LV geometric and myocardial interstitial changes that
influence myocardial diastolic function were examined in
streptozotocin (STZ)(50 mg/kg)-induced diabetes mellitus (DM) in male
rats. After 16 weeks of regular exercise on voluntary running wheels,
cardiac performance was measured in anesthetised, open chest,
ventilated rats. Rats with diabetes mellitus developed a decrease in
LV end diastolic (LVED) chamber and myocardial wall compliance,
associated with an increase in myocardial collagen fluorescence (a
measure of collagen advanced glycosylation end product-AGE
-concentrations), an increase in systemic blood pressure and a dilated
LV. However, LV end systolic elastance and total myocardial
hydroxyproline concentrations were unchanged. Habitual exercise
prevented the augmented LVED chamber stiffness (slope of the
linearised LVEDP-strain relation; DM versus exercise DM;
p<0.01); and myocardial wall stiffness (slope of the linearised
LVED stress-strain relation: DM versus exercise DM; p<0.001)
produced by diabetes mellitus. However, neither markers of blood
glucose control, blood pressure, LV geometry, myocardial
hydroxyproline concentration nor collagen fluorescence were altered
by the exercise program. A reduced LVED chamber and myocardial wall
stiffness, as noted in euglycemic control rats in response to regular
exercise, was also not associated with either hemodynamic or
myocardial interstitial alterations. Therefore, regular, voluntary
exercise opposes the decrement in myocardial diastolic performance
produced by diabetes mellitus in male rats, without influencing the
accumulation of myocardial AGE's thought to be partly responsible for
the stiff myocardium following chronic hyperglycemia. The beneficial
effects of regular exercise on myocardial compliance are likely to be
a consequence of changes in active as opposed to passive properties
of the myocardial wall.
Received 10 January 1996; accepted in final form 22 April 1996.
APS Manuscript Number H7-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96