Dietary Carnitine and Adipose Tissue Turnover Rate in Exercise Trained Rats

Askew, E. W.; Hecker, Arthur L.; Wise, William R.

doi:10.1093/jn/107.1.132

Cited by 39 publications

(7 citation statements)

References 31 publications

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“…The results of the present study confirm and extend a previous report (5) from this laboratory which suggested that endogenous levels of tissue carnitine are adequate to support adipose tissue fatty acid turnover in exercising rats. The results of the present study also indicated that supplementing normal fat diets (28% of the kcal) with carnitine did not result in an increase in the capacity of the enzymes of (3-oxidation to oxidize palmitylcarnitine or the capacity of PCAT to acylate carnitine, the step prior to (3-oxidation.…”

Section: Discussionsupporting

confidence: 91%

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Supplemental Dietary Carnitine and Lipid Metabolism in Exercising Rats

Askew¹,

Dohm²,

Weiser³

et al. 1980

Ann Nutr Metab

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Rats were physically trained by treadmill running and fed normal, high fat, or identical diets supplemented with 1.0% DL-carnitine. Fatty acid oxidation, stimulated by exercise and/or by a high fat diet was studied to determine if it might be further augmented by supplemental dietary carnitine. Fatty acid oxidation in vitro or in vivo was unaffected by carnitine feeding. Carnitine feeding was associated with an increase in heart and muscle palmitylcarnitine acyltransferase activity and reduced serum cholesterol in trained rats fed the high fat diet. Under the conditions of this study, supplemental dietary carnitine did not greatly alter glyceride synthesis, lipolysis, or fatty acid oxidation, which indirectly indicates that the increased demands for fatty acid oxidation resulting from exercise or from fat feeding are adequately supported by endogenous levels of carnitine.

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Section: Discussionsupporting

confidence: 91%

“…Exercise performed on a regular basis increases the mobilization, oxidation, and subsequent turnover of long chain fatty acids (5,20,23). Holloszy (21) has summarized numerous investigations indicating that exercise training increases the reliance of the body's energy generating mechanisms on fat oxidation.…”

mentioning

confidence: 99%

Supplemental Dietary Carnitine and Lipid Metabolism in Exercising Rats

Askew¹,

Dohm²,

Weiser³

et al. 1980

Ann Nutr Metab

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“…Thus, it was appreciated that these results were due to the effect of carnitine as a facilitator of fatty acid oxidation. However, the combination effect of carnitine and other nutrients in beef extract could not be ruled out as suggested by Askew et al (37), which needs to be examined in future studies. For example, it is reported that taurine also decreased body fat (38).…”

Section: Discussionmentioning

confidence: 94%

Beef Extract Supplementation Increases Leg Muscle Mass and Modifies Skeletal Muscle Fiber Types in Rats

Yoshihara

Wakamatsu

Kawabata

et al. 2006

J Nutr Sci Vitaminol

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SummaryThe objective of this research was to investigate the effects of beef extract on fat metabolism, muscle mass and muscle fiber types in rats. We also investigated the synergetic effect of endurance exercise. Twenty-four male rats weighing about 270 g were assigned to two diets containing 0 or 6% beef extract (BE). Half the rats fed each diet were subjected to compulsory exercise (CE) for 30 min every other day. After 4 weeks feeding, the blood was collected and various organs were dissected. The muscle fiber type of the soleus and extensor digitorum longus (EDL) muscles were evaluated by histochemical and electrophoretical analyses. Rats supplemented with BE showed a decrease in fat content in liver and abdomen and an increase in the activity of carnitine palmitoyl transferase II in liver. BE as well as exercise increased the relative weights of both soleus and EDL. BE alone and BE plus CE did not affect the distribution of muscle fiber types in soleus. BE without exercise decreased in type IIb of EDL from 54% to 44% with compensatory increase in type IIa from 41% to 49% and type I from 5% to 7% compared with the nonsupplemented, nonexercised control group. No synergetic effect on a fast to slow fiber conversion due to the combination of BE and CE was detected. Thus, BE supplement increased muscle mass and slow type fiber in EDL. The effects of BE supplement on muscle characteristics were similar to those of exercise. Key Words beef extract, fat metabolism, muscle fiber type, muscle mass, L -carnitine A great deal of research has been done to elucidate the general nutritional value of beef on the growth of human subjects and the effects of protein quality and exercise on the growth and protein metabolism of animals and human beings ( 1-3 ). However, existing information about the nutritional effects of beef extract on muscle metabolism is not sufficient.Skeletal muscle is composed of at least three fiber types on the basis of their contractile and energy metabolic properties; type I fibers exhibit an aerobic energy metabolism (slow-twitch fiber), type IIb fibers are predominantly glycolytic (fast-twitch fiber) and type IIa fibers are the intermediate type exhibiting both oxidative and glycolytic metabolisms. Lipids are easily accumulated in type I fibers ( 4 ), while glycogen depletion occurs primarily in the type II ( 5 ). It is well known that cross-reinnervation, electrical stimulation or exercise evokes the fiber type conversion, although the molecular mechanisms mediating the transformation are not clearly elucidated ( 6 , 7 ). This means that skeletal muscle cells possess a capacity to respond and adapt to metabolic changes imposed by physical stimulation or neural stimulation. Concretely, endurance exercise requiring the consumption of oxygen stimulates a shift to the slow twitch, oxidative muscle fibers ( 8 ). The fiber types of adult skeletal muscle are closely related to energy metabolic characteristics as described above. Nutrition-induced regulation in mRNA levels for a number of metabolic gene...

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“…Stress situations that are characterized by high fatty acid oxidation rates increase carnitine turnover (27,33). Endurance exercise, a special stress situation, and its repetition (training) in rats is associated with increased fatty acid oxidation (2), fatty acid turnover (26), and carnitine turnover (1,33). Several reports also suggest an increased total carnitine utilization in endurance-trained humans (25,32).…”

Section: Introductionmentioning

confidence: 99%

“…It has been hypothesized (2,13,26,27) that the increased fatty acid oxidation and carnitine turnover associated with endurance training could produce a relative carnitine deficiency in rats and humans. In this case, the addition of L-camitine in the diet could increase the potential for fatty acid oxidation and turnover during submaximal exercise.…”

Section: Introductionmentioning

confidence: 99%

Decrease in Respiratory Quotient During Exercise Following L-Carnitine Supplementation

Gorostiaga¹,

Maurer²,

Eclache

1989

Int J Sports Med

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This study was undertaken to determine the effects of L-carnitine addition to the diet during submaximal exercise in endurance-trained humans. Ten subjects (VO2max: 62 ml.kg-1.min-1) performed a control test (C) (45 min of cycling at 66% of VO2max) followed by 60 min of recovery in a sitting position. Each subject repeated this trial after 28 days of placebo (P) and L-carnitine (L-C) treatment (double-blinded cross-over design). The dose of each treatment was 2 g/day. There were no differences between the C and P tests. The respiratory quotient was lower (p less than 0.05) with treatment than with P or C during exercise. In addition, oxygen uptake, heart rate, blood glycerol, and resting plasma free fatty acid concentrations presented a nonsignificant trend toward higher values in L-C than in the C or P groups. These observations suggest an increased lipid utilization by muscle during exercise in the L-C-treated group. This effect has further possibilities for improving performance during submaximal exercise.

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Dietary Carnitine and Adipose Tissue Turnover Rate in Exercise Trained Rats

Cited by 39 publications

References 31 publications

Supplemental Dietary Carnitine and Lipid Metabolism in Exercising Rats

Supplemental Dietary Carnitine and Lipid Metabolism in Exercising Rats

Beef Extract Supplementation Increases Leg Muscle Mass and Modifies Skeletal Muscle Fiber Types in Rats

Decrease in Respiratory Quotient During Exercise Following L-Carnitine Supplementation

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