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Biomedical subjects

E W Askew

Publications and source records attributed to E W Askew.

9 recordsLinked to original sources
PubMed1978

Cyclic AMP metabolism in adipose tissue of exercise-trained rats.

Cyclic AMP metabolism in epididymal adipose tissue of exercise-trained rats was examined to determine if training induced changes in cyclic AMP production or inactivation. Beginning at 7 weeks of age, male rats were physically trained by 12 weeks of treadmill running. Pair-fed control rats remained sedentary in their cages for the duration of the experiment. Tissue levels of cyclic AMP were measured in epididymal adipose tissue slices incubated with norepinephrine. Adenyl cyclase was assayed in adipocyte ghost cell prepartions and low-Km phosphodiesterase was assayed in homogenates of adipose tissue. In response to norepinephrine stimulation, tissue cyclic AMP levels were reduced in trained compared to untrained rats. Training increased the ratio of activity of phosphodiesterase relative to adenyl cyclase. The results of this study indicate that cyclic AMP production in response to norepinephrine stimulation is not increased by training and may even be reduced, implying that adipose tissue cyclic AMP levels may be under a greater degree of control in trained rats. Modulation of adipose tissue cyclic AMP levels may function to regulate more closely the duration of lipolysis in exercise-trained rats.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Adaptation of protein metabolism to endurance training. Increased amino acid oxidation in response to training.

This study was conducted to investigate alterations in excretion of urea and total nitrogen after6-8 weeks of daily exercise and to establish if the capacity for amino acid oxidation in muscle is influenced by endurance training. Urea nitrogen excretion was increased in trained compared with untrained rats and nitrogen balance was less positive in trained than in untrained rats. Increased [14C]leucine oxidation with training was observed both in vivo and in vitro. The results of this study demonstrate that amino acid catabolism is increased during exercise training and that the muscle enzymes involved in leucine oxidation adapt to endurance training in a manner similar to the enzymes of carbohydrate and fat catabolism.

Adaptation, Physiological↗
PubMed1977

Dietary carnitine and adipose tissue turnover rate in exercise trained rats.

Rats trained by 12 weeks of treadmill running were divided into two groups and fed a control diet or an identical diet supplemented with 0.5% L-carnitine. Adipose tissue fatty acid turnover was subsequently estimated by an odd-carbon fatty acid enrichment method utilizing undecanoate as a marker representative of adipose tissue fatty acids. Compared to sedentary untrained control rats, exercise training increased perirenal adipose tissue turnover rate approximately 70%. Trained rats fed the carnitine supplemented diet did not exhibit any further increase in turnover rate. Neither [1-14C]palmitate oxidation by skeletal muscle homogenates nor palmitycarnitine acyl-transferase activity in skeletal muscle mitochondria was affected by carnitine feeding. The results of this study indicate that exercise training increases the turnover rate of adipose tissue fatty acids, but supplemental dietary carnitine does not. Under the conditions of this study, endogenous skeletal muscle carnitine levels in trained rats appear to be adequate to support the rate of fatty acids oxidation incurred by daily treadmill running.

Adipose Tissue↗
PubMed1976

Adipose tissue cell size and lipolysis in the rat: response to exercise intensity and food restriction.

This experiment was designed to determine if the adaptive increase in adipose tissue epinephrine-stimulated lipolysis (ESL) observed in exercise trained rats is related to decreased adipocyte size or a direct response to exercise. Two levels of treadmill exercise and three levels of food restriction were imposed on male rats over a 12 week experimental period to create a distribution of adipose tissue cell sizes. Epinephrine-stimulated lipolysis was subsequently measured in the isolated adipocytes from rats trained at two different exercise levels and in untrained rats fed either ad libitum or 16%, 27%, or 35% dietary restriction. Energy restriction was effective in reducing body weight and to some extent epididymal fat pad weight; however, adipocyte size and number were not significantly affected. Exercise in both groups of trained rats was effective in reducing adipocyte size; however, cell size did not differ between training groups. The group receiving the greatest amount of daily exercise had significantly greater ESL indicating that the adaptive increase in lipolytic potential seen in adipose tissue of exercise trained rats is a true metabolic adaptation not secondary to reduced cell size.

Adipose Tissue↗
PubMed1975

Response of lipogenesis and fatty acid synthetase to physical training and exhaustive exercise in rats.

The effect of physical training and exhaustive exercise on fatty acid synthesis in rat liver and adipose tissue has been investigated. Exercise training (treadmill running) significantly (p less than 0.05) decreased body wt, eipdidymal fat pad wt, adipocyte size, and hepatic fatty acid synthetase activity. Training did not significantly affect adipose tissue cell number, lipogenesis from glucose-U-14C, or fatty acid synthetase. Exercise to exhaustion immediately prior to sacrifice significantly (p less than 0.05) decreased lipogenesis from glucose-U-14C and fatty acid synthetase in adipose tissue from trained but not untrained rats. Liver fatty acid synthetase was not significantly influenced by exhaustive exercise. The results of this study indicate that rats may adapt to physical training by decreasing adipose tissue lipogenesis during exhaustive exercise. This adaptation in energy metabolism may facilitate physically trained animals in conserving blood glucose during exhaustive exercise, thereby prolonging endurance.

Adipose Tissue↗
PubMed1975

Fatty acid and ketone body metabolism in the rat: response to diet and exercise.

This study was designed to measure the response of key enzymes of ketone body metabolism in heart, skeletal muscle, and liver to diet and exercise, two conditions known to influence ketone body utilization. A 3 (diet: control, high fat, or high carbohydrate) X 2 (kill condition: rested or exhausted) X 2 (training: trained or untrained) factorial design was used to estimate main experimental effects as well as identify significant interactions of the variables. Physical training (treadmill running) was associated with a doubling of the activity of skeletal muscle 3-oxoacid CoA transferase, a key enzyme in extrahepatic ketone body utilization. The activity of the rate-limiting enzyme of liver ketone body production, hydroxymethylglutaryl CoA synthetase (HMG CoA synthetase), was not greatly influenced by training or exhuastive exercise indicating that the metabolic control of the ketosis of exercise may more likely be a function of the supply of fatty acids to the liver rather than the activity of HMG CoA synthetase. Feeding a high fat diet, on the other hand, significantly increased the activity of liver HMG CoA synthetase, indicating that the ketosis of fat feeding may be of a different nature than that of exercise. The results of this study indicate that physical training is associated with biochemical adaptations in ketone body metabolism as well as fatty acid oxidation, and that trained individuals are metabolically better endowed to benefit from the ketosis of exercise than untrained individuals.

Acetyl-CoA C-Acetyltransferase↗
PubMed1975

Adipose tissue cellularity and lipolysis. Response to exercise and cortisol treatment.

Male rats a 5 wk of age were subjected to 13 wk of intensive treadmill running to study the effect of exercise on adipose tissue cellularity and lipolysis. Untrained controls of the same age remained sedentary in their cages for the duration of the experiment. Adipocyte numbers were similar in eqidiymal fat pads from trained and untrained rats (12.7 plus or minus 1.3 X 10(6) vs. 15.3 plus or minus 1.3 X 10(6) cells/pad), however trained rats had smaller fat pads containing smaller cells (0.09 plus of minus 0.01 vs. 0.20 plus or minus 0.04 mug triglyceride/cell). Adipocytes from trained rats possessed greater epinephrine-sensitive lipase activity than sedentary rats on a per cell, per milligram protein, per gram adipose tissue, or per fat pad basis. Although the smaller cells of the trained rats had greater epinephrine-sensitive lipase activity than the larger cells of the untrained rats, lipolysis was positively correlated with cell size within both treatment groups. Cortisol treatment of intact animals did not significantly affect in vitro adipose tissue lipolysis. The results of this study indicate that exercise training increased the potential of adipose tissue cells to release free fatty acids in response to epinephrine stimulation. Exercise training initiated at 5 wk of age had only a small effect on adipose tissue cell numbers but significantly decreased cell size.

Adenylyl Cyclases↗