Exercise Training Reverses the Effects of a High Fat Diet on the ACTH Response to Stress

Abstract

PURPOSE: This study was conducted to determine the effects of diet and exercise on the hormone response to stress. We hypothesized that a high fat/high cholesterol diet would compromise the ACTH and cortisol response to stress, and that this decrease would be ameliorated by exercise training. We also hypothesized that exercise training, in animals on a normal control diet, would augment the ACTH and cortisol response to stress. METHODS: Twelve sexually mature, Yucatan miniature swine, aged 9-13 mo, were used for this study. Six animals were placed on a high fat/high cholesterol diet for 16-20 wks and 6 animals received a normal pig chow diet. Three animals from each group underwent treadmill training for 16-20 wks. This distribution of animals resulted in 4 groups with 3 pigs in each group (normal diet sedentary (NS); normal diet exercise training (NEX); high fat/high cholesterol diet sedentary (HFS); high fat/high cholesterol diet exercise training (HFEX)). Blood samples were collected in EDTA Vacutainers while animals were under anesthesia. Anesthesia induces an increase in both ACTH and cortisol in pigs. A two-way ANOVA test of exercise and diet interactions and t-tests were run to compare groups with significance set at P < 0.05. RESULTS: The high fat/high cholesterol diet significantly decreased the ACTH response to anesthesia-induced stress compared to the Controls (NS: 165 ± 22 pg/ml vs. HFS: 79 ± 7 pg/ml). Exercise training did not affect the ACTH response in animals on the normal diet (NEX: 127 ± 17 pg/ml), but significantly increased the ACTH response in the animals on the high fat/high cholesterol diet (HFEX: 230 ± 46 pg/ml). There is a significant interaction between diet and exercise so that the greatest ACTH response was seen in animals receiving both exercise training and a high fat/high cholesterol diet. Neither diet nor exercise affected the cortisol response to anesthesia-induced stress (NS: 116 ± 26 ng/ml; NEX: 106 ± 11 ng/ml; HFS: 140 ± 9 ng/ml; HFEX: 148 ± 30 ng/ml). CONCLUSION: In pigs on a normal chow diet, exercise training does not affect the ACTH or cortisol response to anesthesia-induced stress. A high fat/high cholesterol diet significantly compromises the ACTH response to anesthesia-induced stress and, this decrease is ameliorated by exercise training.