Interactions of iron deficiency and exercise training in male Sprague-Dawley rats: ferrokinetics and hematology

Ferrokinetic and hematologic studies were performed using adult male Sprague-Dawley rats to determine if 12 wk of exercise training alters the delivery of iron to the red blood cell (RBC) mass, the severity of the anemia or the maximal exercise performance of moderately iron-deficient animals. Forty rats were assigned to either iron-deficient (ID) or control (CN) diets, and further subdivided into sedentary (SD) and exercised (EX) groups. Exercised groups were trained on a treadmill, at a 15% grade, 65% VO2max, for 90 min/d, 4 d/wk. After 12 wk of exercise training and dietary iron deficiency, the final body weight of IDEX rats was 90.5% that of IDSD rats. Fractional plasma iron clearance in IDEX rats was 86% of that in IDSD rats (3.32 vs. 2.85%/min). Exercise training failed to increase absolute VO2max (ml/min) or change hemoglobin concentration in iron-deficient rats. Resting oxygen consumption in IDEX rats was 116% that in IDSD rats (42.8 vs. 32.5 ml.kg-1.min-1, P less than 0.05). We conclude that exercise training and iron deficiency interact to alter iron physiology in exercised, iron-deficient animals. This interaction affects the kinetic behavior of plasma iron, growth and basal oxygen consumption.     

Urinary catecholamines in iron-deficient rats at rest and following surgical stress

The purpose of this study was to determine catecholamine concentrations both at rest and in response to a surgical stress in iron-deficient and control rats. Twenty-one-day-old rats were randomized to one of two groups which received a diet containing either 6 or 50 mg iron/kg. Three to five days later, when anemia was first detectable, urinary norepinephrine (NE) concentrations were already significantly elevated in the iron-deficient compared to control rats. In contrast, urinary dopamine (DA) became depressed after 10 days of the iron-deficient regimen. At 38 days of age, both groups were subjected to a surgical stress. NE and DA became elevated over baseline values in both diet groups during the 24-h period following surgery; NE remained significantly higher and DA significantly lower in the iron-deficient than in the control group. We conclude that changes in urine catecholamine concentration occur early in the development of iron deficiency and that they are characteristic of both baseline and stress conditions.     

Effect of nicotine on norepinephrine turnover and thermogenesis in brown adipose tissue and metabolic rate in MSG obese mice

To clarify whether nicotine stimulates the sympathetic nervous system (SNS) and thermogenesis in brown adipose tissue (BAT) and whether it promotes the resting metabolic rate (RMR), with resulting mitigation of obesity, we measured norepinephrine (NE) turnover (an indicator of SNS activity), guanosine-5'-diphosphate (GDP) binding (a thermogenic indicator), oxygen consumption in BAT, and RMR in monosodium-L-glutamate (MSG) obese and saline control mice after 2 weeks treatment with nicotine. Nicotine significantly increased NE turnover, GDP binding, oxygen consumption in BAT, and RMR, and significantly reduced body weight in MSG obese mice as well as in control mice without affecting food intake. These results suggest that nicotine stimulates NE turnover and thermogenesis in BAT, and promotes RMR, all of which contribute to the mitigation of obesity.     

Moderate intensity exercise training improves cardiorespiratory fitness in women

Among women, there is an increased prevalence of sedentary lifestyle and less participation in physical activity at levels recommended by the Surgeon General. As a result, women have been identified as a target group in public health initiatives to increase physical activity. The health-related benefits of habitual, moderate intensity physical activity are well documented in the epidemiological literature, but less is known about the effect of such physical activity on cardiorespiratory fitness. Our hypothesis was that moderate and vigorous exercise training regimens of similar estimated energy expenditure would result in similar changes in cardiorespiratory fitness. Eighteen sedentary premenopausal women with the following baseline characteristics [x +/- SE]: maximal oxygen consumption (Vo2max) = 29.5+/-1.5 ml x kg(-1) x min(-1); age = 33+/-1 years; height = 162.6+/-0.9 cm; mass = 62.7+/-2.3 kg, were randomly assigned to either vigorous (HI, 80% Vo2max, n = 10) or moderate intensity (MOD, 40% Vo2max, n = 8) cycle ergometer training groups. Exercise training was conducted 3-4 (3.37+/-0.05) days/week for 12 weeks in a supervised and progressive manner, with estimated exercise energy expenditure equated across both training groups. Vo2max and time to exhaustion increased significantly in both groups (p<0.05), with no difference between groups. Both groups had lower (p<0.05) posttraining submaximal heart rates (HR), respiratory exchange ratios (RER), and ratings of perceived exertion (RPE) during graded exercise testing, with no significant differences between the groups in posttraining values. Women participating in moderate intensity exercise training as recommended in basic public health guidelines demonstrate an increase in cardiorespiratory fitness similar to that elicited by vigorous training.     

Voluntary resistance exercise improves blood hemoglobin concentration in severely iron-deficient rats

To evaluate the effects of long-term voluntary resistance exercise (climbing) compared with aerobic exercise (swimming) on iron status in severely (4 mg Fe/kg diet) and mildly (18-29 mg Fe/kg diet) iron-deficient rats, we trained male Wistar rats for 8 wk to climb a wire-mesh tower (phi20 cm x 200 cm, CLIMB) and to swim in a plastic pool (phi50 cm x 50 cm, SWIM). These rats were compared with sedentary (SED) rats. After the experimental period, blood hemoglobin level, plasma iron concentration, and transferrin saturation were significantly lower in the 4 mg Fe/kg diet rats than in the 18, 29, and 40 mg Fe/kg diet rats. In 4 mg Fe/kg diet rats, the hemoglobin level was significantly higher in the CLIMB group than in the SED and SWIM groups. On the other hand, neither exercise affected iron status in mildly iron-deficient rats. Bone marrow delta-aminolevulinic acid dehydratase activity was significantly higher in the CLIMB group than in the SWIM and SED groups. These results suggest that long-term resistance exercise is more effective than aerobic exercise in improving blood hemoglobin concentration in severely iron-deficient rats, probably because of an increase in heme biosynthesis. Resistance exercise may be a useful therapy for iron-deficient anemia.     

Effect of chromium supplementation and exercise on body composition, resting metabolic rate and selected biochemical parameters in moderately obese women following an exercise program

OBJECTIVE: To investigate the effect of chromium picolinate (CP) supplementation on body composition, resting metabolic rate (RMR), selected biochemical parameters and iron and zinc status in moderately obese women participating in a 12-week exercise program. METHODS: Forty-four women, 27 to 51 years of age, were randomly assigned to two groups based on their body mass index. Subjects received either 400 microg/day of chromium as a CP supplement or a placebo in double-blind fashion and participated in a supervised weight-training and walking program two days per week for 12 weeks. Body composition and RMR were measured at baseline, 6 and 12 weeks. Selected biochemical parameters and iron and zinc status were measured at baseline and 12 weeks. RESULTS: Body composition and RMR were not significantly changed by CP supplementation. No significant differences in fasting plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or in iron and zinc indices were found between the two groups over time. Serum total cholesterol concentration significantly decreased (p = 0.0016) over time for all subjects combined, probably as a result of the exercise training. Exercise training significantly reduced total iron binding capacity (TIBC) by 3% for all subjects combined (p = 0.001 1). CONCLUSIONS: Twelve weeks of 400 microg/day of chromium as a CP supplement did not significantly affect body composition, RMR, plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or iron and zinc indices in moderately obese women placed on an exercise program. The changes in serum total cholesterol levels and TIBC were a result of the exercise program.     

The effects of diet and exercise training on growth,body composition and blood lipid levels in rats

Adult male Sprague-Dawley rats were fed ad libitum either a high-fat diet or a low-fat diet. Half of the animals from each dietary group were submitted to an exercise regimen consisting of 2 hour swimming bouts, on alternate days for either 4 (Phase I) or 10 (Phase II) weeks. Body weight and food intake were measured weekly, and serum cholesterol levels as well as body composition were determined at the end of the treatment. High-fat diet fed animals ate significantly more food (Phase I 14%, Phase II 15%) weighed more (Phase I 9.5%, Phase II 18.2%) and had more body fat (Phase I 5.1%, Phase II 9.7%) than the low-fat fed controls. Total serum cholesterol (total-C) was greater in high-fat diet animals (Phase I 9 mg/dl, Phase II 30 mg/dl) due to higher levels of cholesterol in all lipoprotein fractions. Exercised animals in both diet groups weighed less (Phase I 13%, Phase II 20%) and had significantly lower levels of body fat (Phase I 4.5%, Phase II 8.2%) than their sedentary counterparts, yet food intake was similar in the two groups. Total-C was less in the exercised animals due to less circulating low density lipoprotein cholesterol (LDL-C) (Phase I 24 mg/dl, Phase II 41 mg/dl) and very low density lipoprotein cholesterol (VLDL-C) (Phase II 4 mg/dl, Phase II 21 mg/dl). Rats exercised for 10 weeks had significantly greater high density lipoprotein cholesterol (HDL-C) (14 mg/dl) than did their sedentary counterparts. The increased HDL-C/total-C ratio observed in both phases was due to the reduction of total-C associated with exercise. Treatments in Phase II had a greater effect on the variables studied than in Phase I, suggesting that time is an important consideration for diet and exercise studies. These results indicate that diet and exercise have independent effects on growth, body composition and serum cholesterol.     

The effect of treadmill exercise on azoxymethane-induced intestinal neoplasia in the male Fischer rat on two different high-fat diets

A total of 120 eight-week-old male rats were exposed to azoxymethane (15 mg/kg body wt in saline s.c.) on Days 1, 4, and 8. Two days after the last injection of carcinogen, the rats were randomized into four experimental groups: two groups were given a chow high in corn oil (23% corn oil) and two groups a chow high in coconut oil (21% coconut oil and 2% corn oil). One group on each chow was kept sedentary, and one group was exposed to moderate exercise, running 2 km/day on weekdays for 38 weeks. At the end of the experiment, the exercising and sedentary rats fed coconut oil were significantly heavier than those fed corn oil. Among the rats fed the high-fat corn oil diet, exercise reduced the number of animals developing carcinomas in the colon (sedentary, 10; exercise, 0) and in the small intestine (sedentary, 5; exercise, 0). The same tendency was observed in the rats fed the coconut oil diet: colon (sedentary, 6; exercise, 3) and small intestine (sedentary, 3; exercise, 2). In the sedentary rats fed the high corn oil diet, 16 intestinal carcinomas were recorded; none were found in the exercised group. In the rats fed the high coconut oil diet, nine carcinomas were recorded in the sedentary groups as opposed to five in the exercised rats. Rats fed the high-fat coconut oil developed significantly fewer neoplasms than the rats fed the equally high-fat corn oil diet.     

Oxidative stress induced by exercise and dietary fat modulates the coenzyme Q and vitamin A balance between plasma and mitochondria.

Physical exercise induces oxidative stress. Dietary fat modulates lipid composition of plasma and fatty acid profile of mitochondrial membranes. Over 8 wk, two groups of rats were fed virgin olive oil or sunflower oil as the only fat sources. Both groups were divided into 4 subgroups according to exercise: one of sedentary rats and the other three of rats subjected to different exercises on a treadmill. There was a lower concentration of vitamin A and coenzyme Q in the plasma of animals subjected to exercise compared to the sedentary animals. The concentrations of these molecules in liver and skeletal muscle mitochondria of animals exercised until exhaustion were higher than in sedentary animals. This can suggest the existence of a balance between plasma and mitochondrial membrane for these antioxidants as a response to an oxidative attack.     

Type of dietary carbohydrate affects thyroid hormone deiodination in iron-deficient rats.

The interactive effect of iron deficiency and dietary carbohydrate type on growth and thyroid hormone status of Sprague-Dawley rats was studied. Rats were fed either an iron-adequate (approximately 35 micrograms Fe/g) or an iron-deficient (less than 3 micrograms Fe/g) diet that contained 70% carbohydrate. The carbohydrate sources were 100% cornstarch (STARCH), 85.7% cornstarch and 14.3% sucrose (STARCH/SUCR), 71.4% cornstarch, 14.3% sucrose and 14.3% dextrin (DEXTRIN), or 100% sucrose (SUCROSE). After 4 wk, iron-deficient rats weighed less than the iron-adequate rats and were severely anemic. Total food intake was lower in iron-deficient than in iron-adequate animals; it was also significantly lower in SUCROSE-fed animals relative to other carbohydrate groups. Plasma glucose concentrations were significantly higher in iron-deficient rats than in iron-adequate rats, but plasma thyroid hormones, thyroxine and triiodothyronine, and liver thyroxine monodeiodinase activity were lower. Deiodination of reverse triiodothyronine in liver was unaffected by iron deficiency regardless of carbohydrate treatment. The STARCH-fed animals had higher rates of hepatic thyroxine monodeiodinase activity than rats fed the other dietary carbohydrates. The two main conclusions from this study are that thyroid hormone metabolism is altered by iron deficiency regardless of food intake and that the best purified rodent diet for this type of study would contain a mixture of carbohydrate types to avoid the stimulation of thyroxine monodeiodinase by a 70% cornstarch diet.     

Iron deficiency hyperlipidemia in 18-day-old rat pups: effects of milk lipids, lipoprotein lipase, and triglyceride synthesis

Three levels of iron (5, 29, 307 ppm iron) were fed to rats from conception through the 18th day of lactation. Dams in the 5 ppm iron group and pups in the 5 and 29 ppm iron groups developed anemia characterized by lower hemoglobin and hematocrit values than control animals. Liver and spleen levels of iron in dams and pups in the 5 and 29 ppm iron groups were lower than in the 307 ppm iron groups. Milk iron was lower in the 5 ppm iron group than in the 29 and 307 ppm iron groups. Pups in the 5 ppm iron group had hyperlipidemia characterized by elevated serum triglycerides, cholesterol, and phospholipids. Milk lipids and post-heparin plasma lipoprotein lipase levels in pups did not differ among experimental groups. Triglyceride and CO2 production from [U-14C]glucose were significantly greater in the iron-deficient pups than in control pups. Hyperlipidemia in 18-day-old iron-deficient rat pups appears to be related to increased endogenous production of triglycerides.     

Effects of habitual physical activity on the resting metabolic rates and body compositions of women aged 35 to 50 years.

OBJECTIVE: To examine the effect habitual physical activity has on resting metabolic rate (RMR) and body composition (fat-free mass[FFM], fat mass, and percent body fat) in active compared to sedentary adult women. DESIGN: RMR was measured (by indirect calorimetry) twice after a 12-hour fast at the same point of the menstrual cycle and 48 hours after exercise. FFM, fat mass and percent body fat were measured using whole body air displacement plethysmography. Energy intake and expenditure were determined using 7-day weighed-food records and activity logs. SUBJECTS: Healthy, weight-stable premenopausal women aged 35 to 50 years classified as either active (approximately 9 hours per week of physical activity for 10 or more years) (n= 18) or sedentary (approximately 1 hour per week of physical activity) (n= 14). STATISTICAL ANALYSES: Analysis of covariance was used to investigate differences in mean RMR (kcal/day) between the groups adjusted for FFM, and independent t tests were used to determine differences in demographic, energy expenditure, and diet variables. RESULTS: Percent body fat and fat mass were lower (P<.0005) and RMR (adjusted for FFM) was significantly higher in the active women (P=.045) compared with sedentary controls. In the active and sedentary groups respectively, mean adjusted RMR was 1,510 kcal/day and 1,443 kcal/day, body fat was 18.9% and 28.8%, and fat mass was 11.1 kg and 18.8 kg. Groups were similar in body mass, FFM, body mass index, and age. Mean energy balance appeared to be more negative in the active group (P=.0059) due to significantly higher mean self-reported energy expenditures (P=.0001) and similar mean self-reported energy intakes (P=.52) compared with sedentary controls. These data indicate that active women who participate in habitual physical activity can maintain lower body fat and a higher RMR than sedentary controls with similar body mass, FFM, and body mass index. APPLICATIONS/CONCLUSIONS: This research supports and emphasizes the benefits of habitual physical activity in maintaining RMR and lower body fat levels in middle-aged women.     

Diet and gene interaction.

Objective: To investigate the effect of chromium picolinate (CP) supplementation on body composition, resting metabolic rate (RMR), selected biochemical parameters and iron and zinc status in moderately obese women participating in a 12-week exercise program.

Methods: Forty-four women, 27 to 51 years of age, were randomly assigned to two groups based on their body mass index. Subjects received either 400 μg/day of chromium as a CP supplement or a placebo in double-blind fashion and participated in a supervised weight-training and walking program two days per week for 12 weeks. Body composition and RMR were measured at baseline, 6 and 12 weeks. Selected biochemical parameters and iron and zinc status were measured at baseline and 12 weeks.

Results: Body composition and RMR were not significantly changed by CP supplementation. No significant differences in fasting plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or in iron and zinc indices were found between the two groups over time. Serum total cholesterol concentration significantly decreased (p = 0.0016) over time for all subjects combined, probably as a result of the exercise training. Exercise training significantly reduced total iron binding capacity (TIBC) by 3% for all subjects combined (p = 0.0011).

Conclusions: Twelve weeks of 400 μg/day of chromium as a CP supplement did not significantly affect body composition, RMR, plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or iron and zinc indices in moderately obese women placed on an exercise program. The changes in serum total cholesterol levels and TIBC were a result of the exercise program.     

Iron deficiency: improved exercise performance within 15 hours of iron treatment in rats

We tested the hypothesis that a very rapid improvement in exercise performance of iron-deficient rats after treatment with iron might reveal a rate-limiting role of ionic iron as an enzyme cofactor in energy metabolism. Rats were given iron-deficient or control diets after weaning at 21 d of age and intraperitoneal iron dextran (50 mg/kg) at 45 d of age. Time to fatigue during an easy walking exercise (endurance) was measured 15 and 18 h after iron dextran or saline injection. Endurance increased more than threefold compared to the saline-treated, iron-deficient animals without a significant change in hemoglobin concentration. This prompt improvement suggests that lack of cofactor iron might play a metabolically important role in impairing exercise performance in the severely iron-deficient rat.     

The effects of exercise on milk yield, milk composition, and offspring growth in rats

This study examined effects of exercise training throughout pregnancy and lactation upon selected indicators of lactational performance in Wistar rats. During the 7 wk prior to mating, experimental female rats were gradually trained to swim for 2 h/day, 5 days/wk with a 3% tail weight; they continued swimming until the 19th day of pregnancy. Control animals remained sedentary. Swimming resumed during days 2-14 of lactation. Food intake was greater in exercised rats during the lactation period. Body weights of the two groups were comparable. Mild yield (day 10), energy content (day 15), and protein and fat concentrations did not differ, but milk of exercised rats had a lower lactose concentration. The exercise regimen had no statistically significant effect on litter size or on offspring weight to day 15. This study indicates that moderate-intensity, aerobic exercise does not markedly affect the lactational performance of ad libitum-fed rats.     

Tumor growth reduction in Walker 256 tumor-bearing rats performing anaerobic exercise: participation of Bcl-2, Bax, apoptosis, and peroxidation

Physical activity has been used in cancer prevention and treatment. In this study, we investigated some of the mechanisms by which anaerobic exercise reduces tumor growth. To do so, rats were trained for 8 weeks. Training consisted of jumping in a swimming pool for ten 30-s sets, with a load that was 50% of body weight attached to the back, 4 times per week. At the sixth week, anaerobic exercise trained rats (EX group) were inoculated with a suspension of Walker 256 tumor cells. Tumor weight, apoptotic tumor cells, tumor Bax and Bcl-2 protein expression, tumor lipid peroxidation, and tumor cell proliferation ex vivo were evaluated. Tumor weight was significantly lower in the EX group (～30%) than in rats that did not undergo training (sedentary group) (p < 0.05). Apoptosis in the tumor cells of EX rats was 2-fold higher than in the tumor cells of sedentary rats; in addition, Bax expression increased by 10% and Bcl-2 decreased by 13% in EX rats. Lipid peroxidation was 4-fold higher in the tumor cells of EX rats than in those of sedentary rats (p < 0.05). Tumor cell proliferation ex vivo was 29% lower in the EX group than in the sedentary group (p < 0.05). In conclusion, Walker 256 tumor-bearing exercised rats presented more tumor cell apoptosis, a higher tumor content of lipid peroxides, pro-apoptotic protein expression balance, and reduced tumor weight and cell proliferation ex vivo, compared with sedentary rats. These events, together, account for the lower tumor growth we observed in the EX rats.     

Evidence for thyroid hormone deficiency in iron-deficient anemic rats

Iron-deficient anemic rats have previously been shown to have low plasma levels of thyroid hormone and a poor plasma thyroid hormone response to acute cold exposure. As an initial exploration, we examined thyroid hormone metabolism during iron deficiency in age-matched rats from three aspects: 1) plasma TSH (thyrotropin, thyroid stimulating hormone), T4 (thyroxine) and T3 (triiodothyronine) responses to graded doses of exogenous TRH (thyrotropin releasing hormone), 2) plasma T3 kinetics, and 3) rates of hepatic T3 production. Iron-deficient anemic rats had lower basal TSH values and blunted TSH responses to intravenous TRH injection at three different doses (10, 25 and 50 ng TRH/100 g body wt). Iron-deficient anemic rats also had a significant decrease in plasma T3 turnover (42 vs. 88 ng/h in controls), and significantly lower hepatic T4-5'-deiodinase activities than controls [26 vs. 44.0 ng T3/(mg protein.20 min)]. Thus, decreased rates of T3 production in iron-deficient anemic rats, as documented by turnover studies, may be related to decreased deiodinase activity and reduced peripheral formation of T3. The dampened TSH responses to TRH further facilitate or perpetuate this T3 deficiency. We propose that this abnormal thyroid state is partially responsible for impaired thermogenesis in iron-deficiency anemia.     

Effects of voluntary running exercise on blood pressure and renin-angiotensin system in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats

The effect of a voluntary running exercise on blood pressure and renin-angiotensin system (RAS) was studied in male spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). SHR and WKY were assigned to either voluntary running exercise or sedentary control groups at 5 wk of age. The systolic blood pressure in the exercised group for both strains of rats was significantly lower than in the sedentary control group. The plasma renin activity (PRA) and plasma renin concentration (PRC) were significantly lower in voluntary running exercised SHR than in sedentary SHR, whereas the same exercise did not result in a lower PRA and PRC in WKY. These results suggested that the blood pressure lowering effect of voluntary running exercise is related to the suppression of RAS in SHR.     

Physical activity and resting metabolic rate

The direct effects of physical activity interventions on energy expenditure are relatively small when placed in the context of total daily energy demands. Hence, the suggestion has been made that exercise produces energetic benefits in other components of the daily energy budget, thus generating a net effect on energy balance much greater than the direct energy cost of the exercise alone. Resting metabolic rate (RMR) is the largest component of the daily energy budget in most human societies and, therefore, any increases in RMR in response to exercise interventions are potentially of great importance. Animal studies have generally shown that single exercise events and longer-term training produce increases in RMR. This effect is observed in longer-term interventions despite parallel decreases in body mass and fat mass. Flight is an exception, as both single flights and long-term flight training induce reductions in RMR. Studies in animals that measure the effect of voluntary exercise regimens on RMR are less commonly performed and do not show the same response as that to forced exercise. In particular, they indicate that exercise does not induce elevations in RMR. Many studies of human subjects indicate a short-term elevation in RMR in response to single exercise events (generally termed the excess post-exercise O2 consumption; EPOC). This EPOC appears to have two phases, one lasting < 2 h and a smaller much more prolonged effect lasting up to 48 h. Many studies have shown that long-term training increases RMR, but many other studies have failed to find such effects. Data concerning long-term effects of training are potentially confounded by some studies not leaving sufficient time after the last exercise bout for the termination of the long-term EPOC. Long-term effects of training include increases in RMR due to increases in lean muscle mass. Extreme interventions, however, may induce reductions in RMR, in spite of the increased lean tissue mass, similar to the changes observed in animals in response to flight.     

Effect of exercise on tissue lipids and serum lipoproteins of rats fed two levels of fat.

Adult rats were fed a low fat (4%) or a high fat (40%) diet, and groups of other rats selected for good running were fed these two diets and were treadmill exercised 5 days a week for 6 weeks. The serum triglycerides were significantly lower in exercised rats fed the low fat diet, but not in those fed the high fat diet, as compared with corresponding controls. The liver lipids were vastly elevated in sedentary rats fed the high fat diet as compared with those fed the low fat diet. An interesting effect of exercise was reflected by the near normal liver lipid levels in rats fed the high fat diet and exercised. However, in these animals, the muscle concentration of cholesterol was significantly higher than that in all other groups. The very low density lipoproteins tended to be lower while the low density lipoproteins tended to be greater in exercised as compared with sedentary rats. It was suggested that the decline in very low density lipoproteins was due to decreased synthesis resulting from adaptive changes in the exercised animal. It was further postulated that the increase in low density lipoproteins was possibly due to increased synthesis necessitated by the need to enhance the catabolism and excretion of cholesterol in exercised animals.