The effect of exercise and exercise training on fat oxidation in older adults

The purpose of this dissertation was to determine if fat oxidation was reduced in elderly and to investigate the impact FO has on immune responses to stress (exercise), and finally the benefits and consequences of statin therapy. The following hypotheses were tested: (1) Elderly will have reduced fat oxidation, even after correction for the reduced maximal aerobic power, compared to young subjects. (2) The reduced fat oxidation in the elderly will be associated with reduced release and uptake of fats for metabolism, compared to young. (3) Aerobic exercise training in the elderly will improve fat oxidation, but will not reach the same level as the young. (4) Elderly will have an exaggerated immune response to exercise stress, which will be reduced by exercise training. (5) Statin therapy will significantly reduce fat oxidation.;In the first study, total body FO during progressive VO2max test on a cycle ergometer in sedentary young and elderly subjects was compared and then the effect of aerobic exercise training on FO in elderly determined. For the second study, FO, VO2max, blood lipids, and the immune response to exercise in elderly (N=14) compared to young (n=16) and elderly prior to and after aerobic exercise training (12 wks, 3 sessions/wk for 1 hr). For the last study, elderly on statin therapy (n = 14) were compared to elderly control subjects (n = 14). FO was determined during maximal and sustained submaximal exercise protocol.;VO2 and RER increased linearly with exercise intensity for young and elderly. At submaximal VO2, RER increased as a function of VO2, and in elderly the slope increased significantly more than young. Exercise training in elderly increased VO2max (20% in elderly women, 30% in elderly men) and decreased RER at submaximal VO2 in elderly men (RER = 0.21 VO2 + 0.75), but not for elderly women. These data were confirmed in the second study where young had significantly higher VO2max than elderly. Young had longer sustained exercise duration (45.5 +/- 17.6 min) than elderly pre-training (30.2 +/- 14.0 min). After 12 weeks of aerobic training in elderly, there was a significant increase in VO2max (14.53 +/- 3.68 to 24.54 +/- 4.57 ml/min/kg, p = 0.001). After training, fasting total cholesterol and low density lipoprotein cholesterol did not change, while triglycerides (TG) increased. After the VO2max test, post-training, RER and blood lactate were significantly lower, while glucose increased. TG increased by the VO2max test (10-15%) both pre and post-training. After training, submaximal exercise time, glucose, and TG increased, while RER was reduced. Although total caloric intake was higher in young, the balance of carbohydrates, fats and proteins was similar in young and elderly (about 53, 26 and 19%, respectively). There were no differences between cytokines in young and elderly subjects (p = 0.38 to 0.63). For elderly there were no significant effects of exercise on IL-1beta, IL-6 or IL-10 after 12 weeks of training. In the last study, RER was significantly higher in subjects taking statins during both the VO2max and submaximal tests, indicating reduced FO. Blood lipoprotein levels during exercise were not affected by statins nor were levels of glucose, lactate, or TG. However, free fatty acid levels were significantly elevated by exercise. Statin therapy did not affect IL-1beta or TNF-alpha, but increased IL-6.;FO was reduced in the elderly before training, and remained lower than young even after VO2max and FO were increased after training, particularly in women. Elderly did not have reduced fat availability from blood or FO after correction for VO2max during exercise on a treadmill, which increased after training; and sustained exercise duration increased; however this 12 week aerobic training had little effect on the cardiovascular risk factors measured in this study. Neither young nor elderly healthy untrained subjects demonstrated inflammatory responses to exercise and training. In addition, cytokine production was not significantly altered in elderly. It appears that factors other than age may negatively impact the immune system in elderly subjects, i.e. diet, inactivity, diseases, etc. Although statin therapy lowers baseline blood lipoproteins, its secondary effects need further consideration as FO was significantly reduced in elderly, and this could not be accounted for by diet, exercise, fitness or availability of fat from the blood. (Abstract shortened by UMI.).