THE SWINE AS A MODEL FOR STUDYING EXERCISE-INDUCED CHANGES IN LIPID-METABOLISM

The swine has many similarities to humans, making it an excellent rese arch model in which to study the role of exercise on lipid metabolism. Swine adapt to exercise-training by increasing muscle oxidative enzym es, maximal stroke volume, cardiac output, (V) over dot O-2max, and hi gh density lipoprotein cholesterol levels, while decreasing total chol esterol levels and resting heart rate. The lipoprotein profile of swin e and humans is also similar, and low density lipoprotein is the major cholesterol transporting lipoprotein in both species. Several studies in swine report conflicting results on the effect of exercise-trainin g on lipoprotein profile and atherosclerotic lesion appearance. This m ay result from differences in total exercise time between the studies. With sufficient total exercise, atherosclerosis was reduced and high density lipoprotein cholesterol levels were increased. Exercise may al so play a role in reducing obesity, a risk factor for cardiovascular d isease, by enhancing lipid mobilization from adipocytes. Recent resear ch suggests that swine adipocyte sensitivity to adenosine, a locally-p roduced antilipolytic agent, is reduced after exercise treatment. Cell ular mechanisms responsible for this metabolic change include a reduct ion in adenosine A(1) receptor number. Current studies are examining t he transport of extracellular cyclic AMP from adipocytes and its role as a potential adenosine precursor.