EXERCISE, STRESS AND ATHEROSCLEROSIS

We will expose 18 adult male baboons to chronic psychosocial stress, diet
induced hyperlipidemia, and diet induced elevation in bold pressure in
order to test the hypothesis that program of graded aerobic exercise
results in decreased extent and severity of experimentally induced
atherosclerosis. We will examine the combined effects of stress and graded
aerobic exercise on atherosclerosis in an animal model, where environmental
and nutritional variables are controlled while neuroendocrine, metabolic
and psysiologic variables are measured by means of an instrumented tether
system. This experiment is designed to provide initial answers for two
interrelated questions: (1) does exersise ameliorate the adverse effects
of stress, diet and aggressive behavior on atherosclerosis, and (2) what
are the underlying physiologic, metabolic, neuroendocrine and behavioral
mechanisms by which exercise modfiies the effects of psychosocial stress on
atherosclerosis. The experiment uses: (1) resistance of stable social
organization (dyadic coalitions) to the introduction of intruders, (2)
perturbation of a stable social dominance hierarchy by intruders as a model
of social stress; (3) graded work on a treadmill as a model of exercise;
(4) baboons who will be fed on atherogenic diet; and (5) an instrumented
tether system that allows us to obtain measurement of cardiovascular and
biochemical variables in fully conscious baboons who are unrestrained
within the confines of their cage. The three experimental treatment groups
consist of sedentary (n=6), light exercise (n=6) and moderate exercise
(n=6). We will measure cardiovascular function in terms of heart rate,
systolic, diastolic and mean blood pressure using an indwelling
catheter/transducer; circulating mediators of cardiovascular function
(plasma renin, electrolytes and vasopressin); hormonal indicators of
sympathetic system arousal and stress response (plasma catecholamines,
cortisol, and testosterone); aggressive behavior (tension, threat, attack);
physioloigcal indicators of exercise (blood lactate, muscle papillary
density and enzyme activity) and lipids (serum cholesterol, HDL, LDL and
VLDL cholesterol). The animals will be autopsied and the hypotheses tested
with respect to the effects of exercise, physiologic, metabolic and
behavioral variables on atherogenic lesion.