Date of Award

Spring 1988

Project Type

Dissertation

Program or Major

Animal and Nutritional Sciences

Degree Name

Doctor of Philosophy

First Advisor

Samuel C Smith

Abstract

The effects of chronic, endurance exercise on the concentration of plasma lipids and on the composition and metabolism of plasma lipoproteins were examined in Yucatan miniature swine following more than two years of intensive exercise training. The exercise protocol employed produced significant training effects, as indicated by enhanced cardiovascular and aerobic capacities. Lipoprotein lipase and hepatic triglyceride lipase activities were also significantly increased in the exercised group. Neither total plasma cholesterol nor triglycerides differed between the two groups. Total high-density lipoprotein cholesterol (HDL) was not significantly greater in the exercised swine; however, exercise was associated with a shift in the distribution of cholesterol from the HDL-three to the HDL-two subfraction. The significant rise in HDL-two cholesterol was strongly correlated with the rise in lipoprotein lipase. Compositional analyses of the major lipoprotein classes indicated several exercise-induced shifts, especially in cholesteryl ester, free cholesterol and triglyceride content.

These studies also clearly demonstrated the presence of heterogenous low-density lipoproteins (LDL) which differed in lipid composition. Significant increases in the total lipid mass of LDL-one and LDL-two were observed in the exercised swine, perhaps reflecting the demonstrated alterations in lipoprotein lipase. Exercise had little effect on the fractional catabolic rates or production rates of either LDL subclass; hence, control and exercise data were pooled in order to better assess the kinetic characteristics of LDL subclasses in the swine model. It appears that LDL-one is the more metabolically active subclass since its fractional catabolic rate and production rate were significantly higher than those of LDL-two. Exercise also appeared to have little effect on the mass of Apoproteins E or C, or any of their isoforms. Furthermore, the Apoprotein E/C, C-II/C-III and E/C-III ratios were not influenced by exercise.

In toto, the results of these studies suggest that physical exercise is associated with subtle but significant changes in plasma lipids and lipoproteins, which are consistent with a reduced risk or coronary heart disease.

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